9 770268 451128
0
L 1
[ •
r.
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Choke A Chicken
GT-3095 £8.50 + post & packing
Relieve stress with a bit of
violence! This annoying chicken
dances around and squawks.
Funny for about one second!
Grab him by the throat and
he screams and gags.
Funny forever! (not
recommended for ^
children). Approx 12" ^
tall. Requires 4 x AA
batteries (not ind.)
1
Theremin Synthesiser Kit
KC-5295 £14.75 + post & packing
The Theremin is
a weird musical
instrument that was
invented early
last century
but is still
used today.
The Beach
Boys' classic
hit "Good
Vibrations" featured
aTheremin. By moving you hand
between the antenna and the metal
plate, you can create strange sound
effects. Kit includes a machined, silk
screened, and pre drilled case, circuit
board, all electronic components, and
clear English instructions.
We Stock...
Electronic Components,
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Audio 61 Visual Equipment
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Call or log on to our website and apply for a FREE
400 page catalogue. You can purchase on the Net
from us 24/7/365 through our secure encrypted
system. Post and packing charges are modest and
you can have any of 8000+ unique products
delivered to your door within
Smart Card Reader/ 7-10 days of your order.
Programmer Kit
KC-5361 £15.95 + post & packing
Jaycar has noticed a substantial increase in sales of
the KC-5361 Smart Card Programmer Kit &
ZZ-8800 Programmable Gold Wafer Card. We
strongly suspect that this maybe due to persons
unknown some how using these products to make
unlawfully generated access codes for the latest
cable T.V. set top boxes. We also wish to advise
that we discourage this activity. For those
legitimate users, the KC-5361
Programmer Kit £15.95 &
ZZ-8800 Smart Card £3.85
are back in stock.
Once again please be
reminded that we cannot
accept any responsibility for
the use of these devices in
other than legitimate
activities.
Wafer Card
ZZ-8800 £3.85 + post & packing
This is a multi-chip 'smart card' based
on the PIC 16F84A and is coupled
with a 24LC16B EEPROM,
compatible with most
reader/programmer units
available including the
programmer above.
"Clock Watcher's" LED Clock Kits
KC-5416(blue) £55.25 + post & packing
KC-5404(red) £41.35 + post & packing
These clocks are hypnotic!
They consist of an AVR driven clock circuit, that also
produces a dazzling display with the 60 LEDs around the
perimeter. It looks amazing, but can't be properly explained
here. We have filmed it in action so you can see for yourself
on our website www.jaycarelectonics.com! Kit supplied with
double sided silkcreened plated through hole PCB and all
board components
as well as the
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Available
in Blue
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High Performance Electronic Projects for Cars
BS-5080 £7.00 + post & packing
Australia's leading electronics magazine Silicon Chip, has developed a range of projects for performance
cars. There are 16 projects in total, ranging from devices for remapping fuel curves, to nitrous controllers.
The book includes all instructions, components lists, color pictures, and circuit layouts. There are also
chapters on engine management, advanced systems and DIY modifications. Over 150 pages! All the
projects are available in kit form.
Smart Fuel Mixture Display
KC-5374 £8.95 + post & packing
This new 'smart' version has a few additional touches
such as, auto dimming for night driving, emergency
lean-out alarm, and better circuit protection. Another
great feature, is the 'dancing' display which operates
when the ECU is operating in closed loop. Kit supplied
with PCB and all electronic components.
• Car must be fitted with air flow
and EGO sensors (standard ^
on all EFI systems)
for full
functionality.
Recommended box
HB-6014 £1.40 each
High Range Adjustable j
Temperature Switch with LCD
KC-5376 £22.75 + post & packing
Heat can be a major problem with
any car, especially modified and
performance cars. The more power,
the more heat, so you need to
ensure you have adequate cooling
systems in place. This temperature
switch can be set anywhere up to
2192°F, so it is extremely versatile. The
relay can be used to trigger an extra
thermo fan on an intercooler, mount a sensor
near your turbo manifold and trigger water spray
cooling, or a simple buzzer or light to warn you of a
high temperature. The LCD displays the temperature
all the time, which can easily be dash mounted.
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aycar
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Log on to
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(Monday - Friday 09.00 to 17.30 GMT + 10 hours only).
For those who want to write:
100 Silverwater Rd Silverwater NSW 2128
Sydney AUSTRALIA
FT232R usb uart with
MCU Clock Generator and
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I/O Drive Capability - from 5.5v down to 1 .8v levels at
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I/O Modes - synchronous and asynchronous Bit-Bang
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for Windows 98,ME,2K, Server 2003, XP, XP64,
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Driver Options - VCP and D2XX drivers for all
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Technical Support - a wide range of evaluation kits
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Board Space - new QFN package takes up only
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Programming - FT232R comes pre-programmed with
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Micros turn Mega
acting the way
I've always been confident that the Greek
prefixes |j (micro) and M (mega) are
safely apart at an immense factor of 1 0 1 2
or one bin ion. The venerable prefixes are
established in electronics to the extent that
only rank beginners would surmise the
existence of microhertz frequencies and
megafarad capacitances. Sure, these
exist in theory but no-one's ever seen the
equipment or capacitor to match.
Although it's not necessary right now to
burn your maths textbooks, recently the
distance between micro and mega has
dwindled and in fact both prefixes can
now be said to co-exist happily in two
species of electronic component. The
main subjects of this month's issue,
microcontrollers and FPGAs, execute
microinstructions from megabytes of
memory, not forgetting nanosecond sig-
nal setup times and several kilobits a sec-
ond worth of data traffic on serial lines.
If you thought that the microcontroller
was the next and perhaps final step in
an evolutionary process that started with
the valve and went by way of the tran-
sistor and the integrated circuit, buckle
up for FPGAs. To illustrate the scale at
which we need to think now, some
FPGAs are powerful enough to mimic a
vintage 6502 microprocessor including
its exact pin functionality, and still have
room to spare for 'side activities' like
serial interfacing and memory flashing.
Readers tell us that they find FPGAs
impressive and even awe-inspiring, but
also off putting not just for design com-
plexity but mostly 'solderability'!
Here at Elektor Electronics we're not in
the least afraid to deal with the latest in
FPGA and microcontroller land, witness
our Versatile FPGA Module, FPGA Pro-
totyping Board and Renesas R8C/13
Motherboard. Let the professionals do
the soldering — in all three cases we
supply the boards with all the dreaded
SMDs, BGAs and TQFPs and what have
you ready fitted, so you can concentrate
on the real thing: programming and
developing turnkey applications with
maximum intelligence and an absolute
minimum of components. I wouldn't say
wielding a full-blown FPGA or R8C
development system is a micro effort at
a nano investment but you can be cer-
tain of mega results. Glad to help you.
Jan Baiting
Editor
16
Until recently, FPGAs were
practically reserved for
specialists in high-tech
companies. That's all
changed now thanks to low
component prices and free
design software, so it's high
time to devote attention to
this technology in Elektor
Electronics. The FPGA
module discussed in this
article forms the core of
various upcoming projects
in the magazine.
Versatile
FPGA Modu
Free C Booklet
Th is issue comes with a free 24-
page introduction to C pro-
gramming. The booklet is not
only a runway to an industry-
standard programming lan-
guage, but also a prelude
to articles on C for our
low-cost R8C Starter Kit.
CONTENTS
Volume 32
March 2006
no. 352
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We devote attention to interesting but affordable
kits where we not only look at kits that are suitable
for a commercial environment but which are also
very interesting for hobby use.
28 Development Kits
38 Application Board for R8C/1 3
Last month we described how you can get started with our
under-£10 R8C/1 3 microcontroller module. The Now we
add a 'base camp' with lots of con-
nections to the outside world like
USB, two serial ports and an
LCD interface.
know-how
68 Linear Motors
hands-on
16 Versatile FPGA Module
20 FPGA Prototyping Board
38 Application Board for R8C/13
46 Cheap Logger
54 A real pC PLC
63 Telephone Eavesdropper
Design Tips
Energy recovery
FBI siren with flashing light
Energy saver for relays
Opamp with increased output current
technology
50 Travel Charger
58 E-blocks Making Waves
info & market
6 Colophon
8 Mailbox
Corrections & Updates
News & New Products
28 Development Kits
74 The 'Kaleidoscope'
E-CAD DVD
84 Sneak Preview
infotainment
34 The Triumphant March
of the 6502
Retronics:
Elektor Plotters (1 988-1 991 )
79 Hexadoku (3)
lektor
lectronics
Volume 32, Number 352, March 2005 ISSN 0268/45 1 9
Elektor Electronics aims at inspiring people to master electronics at any person-
al level by presenting construction projects and spotting developments in elec-
tronics and information technology.
Publishers: Elektor Electronics (Publishing), Regus Brentford, 1000 Great West Road,
Brentford TW8 9HH, England. Tel. (+44) (0) 208 261 4509, fax: (+44) (0) 208 261 4447
www.elektor-electronics.co.uk.
The magazine is available from newsagents, bookshops and electronics retail outlets, or on sub-
scription. Elektor Electronics is published I I times a year with a double issue for July & August.
Under the name Elektor and Elektuur, the magazine is also published in French, German and
Dutch. Together with franchised editions the magazine is on circulation in more than 50 countries.
International Editor: Mat Heffels (m.heffels@segment.nl)
Editor: Jan Buiting (editor@elektor-electronics.co.uk)
International editorial staff: Harry Baggen, Thijs Beckers, Ernst Krempelsauer,
Jens Nickel, Guy Raedersdorf.
Design staff: Ton Giesberts, Paul Goossens, Luc Lemmens, Karel Walraven
Editorial secretariat: Hedwig Hennekens (secretariaat@segment.nl)
Graphic design / DTP: Ton Gulikers, Giel Dols
Managing Director / Publisher: Paul Snakkers
Marketing: Margriet Debeij (m.debeij@segment.nl)
Subscriptions: Elektor Electronics (Publishing),
Regus Brentford, 1000 Great West Road, Brentford TW8 9HH, England.
Tel. (+44) (0) 208 26 1 4509, fax: (+44) (0) 208 26 1 4447
Internet: www.elektor-electronics.co.uk
Email: subscriptions@elektor-electronics.co.uk
Rates and terms are given on the Subscription Order Form
Head Office: Segment b.v. RO. Box 75 NL-6I90-AB Beek The Netherlands
Telephone: (+31)46 4389444, Fax: (+31)46 4370161
Distribution: Seymour, 86 Newman Street, London Wl P 3LD, England
UK Advertising: Huson International Media, Cambridge House, Gogmore Lane,
Chertsey, Surrey KTI 6 9AR England.
Telephone: +44 (0) 1 932 564999, Fax: +44 (0) I 932 564998
Email: r.elgar@husonmedia.com
Internet: www.husonmedia.com
Advertising rates and terms available on request.
International Advertising: Klaas Caldenhoven, address as Head Office
Email: advertenties@elektuur.nl
Advertising rates and terms available on request.
Copyright Notice
The circuits described in this magazine are for domestic use only. All drawings, photographs, printed circuit
board layouts, programmed integrated circuits, disks, CD-ROMs, software carriers and article texts pub-
lished in our books and magazines (other than third-party advertisements) are copyright Segment, b.v. and
may not be reproduced or transmitted in any form or by any means, including photocopying, scanning an
recording, in whole or in part without prior written permission from the Publishers. Such written permis-
sion must also be obtained before any part of this publication is stored in a retrieval system of any nature.
Patent protection may exist in respect of circuits, devices, components etc. described in this magazine. The
Publisher does not accept responsibility for failing to identify such patent(s) or other protection.
The submission of designs or articles implies permission to the Publishers to alter the text and design, and
to use the contents in other Segment publications and activities. The Publishers cannot guarantee to return
any material submitted to them.
Disclaimer
Prices and descriptions of publication-related items subject to change. Errors and omissions excluded.
© Segment b.v. 2006 Printed in the Netherlands
£
a>
lectronics
cd-rom Elektor 2005
This CD-ROM contains all editorial
articles, with the exception of New
Products items, published in Elektor
Electronics magazine Volume 2005.
Using the supplied Acrobat Reader
program, articles are presented in
the same layout as originally found in the magazine.
The DiskMirror utility on this CD-ROM allows your earlier Elektor
year volume CD-ROMs (1997-2004) to be added to a large archive
on hard disk for fast access and easy reference.
A built-in search function allows you to find references in any article
from the archive on hard disk, or from individual year volume
CD-ROMs you have available.
6
elektor electronics - 3/2006
SERIAL COMMUNICATIONS SPECIALISTS
Test and Measurement Solutions
featured products
= = = Bronze Prize Winner = =
NASA Tech Briefs 2004
Products of the Year
£125.00
DS1 Ml 2 USB Scope / Logger
2x1 MS/s Input Channels + waveform
generator output. EasyScope & EasyLogger s/w
included.
Affordable CAN Bus Solutions
CANUSB is a very small dongle that plugs into any PC USB Port
and gives an instant CAN connectivity. This means it can be treated
by software as a standard COM Port (serial RS232 port) which
eliminates the need for any extra drivers or by installing a direct
driver DLL for faster communications and higher CAN bus loads.
CAN232 is a very small dongle that plugs into any PC COM Port, or
any other RS232 port in an embedded system and gives an instant
CAN connectivity. This means it can be treated by software as a
standard COM Port (serial RS232 port) which eliminates the need
for any extra drivers. Sending and receiving can be done in standard
ASCII format.
priced from £61 .00 (CAN-232)
USB Instruments - PC Oscilloscopes & Logic Analyzers
Our range of PC Instruments may be budget priced but have
a wealth of features normally only found in more expensive
instrumentation. Our DS1M12 and PS40M10 oscilloscopes have
sophisticated digital triggering including delayed timebase and come
with our EasyScope oscilloscope / spectrum analyzer / voltage
and frequency display application software and our EasyLogger
data logging software. We also provide Windows DLLs and code
examples for 3rd party software interfacing to our scopes.
OurANT8 and ANTI 6 Logic Analyzers feature 8/16 capture channels
of data at a blazing 500MS/S sample rate in a compact enclosure.
priced from £125.00 ( DS1M12 & ANT8 )
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USB-2C0M-
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mount bracket and DC auxiliary output
1 to 16 port USB to Serial Adapters
With over 16 different models available, we probably stock the
widest range of USB Serial Adapters available anywhere. We offer
converter cables, multi-port enclosure style models in metal and
plastic, also rack mount units with integral PSU such as the USB-
16COM-RM. Serial interfaces supported include RS232, RS422 and
RS485. We also supply opto-isolated RS422 and RS485 versions for
relaible long distance communications. All our USB Serial products
are based on the premium chipsets and drivers from FTDI Chip for
superior compatibility, performance and technical support across
Windows, MAC-OS, CE and Linux platforms.
priced from £20.00 ( US232B/LC )
UPCI Serial Cards
Discover our great value for money range of multi-port UPCI serial
cards. Supporting from two to eight ports, the range includes RS232,
RS422, RS485 and opto-isolated versions. Our 4 port and 8 port
models can connect through external cables or the innovative wall
mounting COMBOX.
priced from £21.00 ( UPCI - 200L )
EasySync Ltd
373 Scotland Street
Glasgow G5 8QB U.K.
Tel: +44 (141)418-0181 Fax: +44 (141)418-0110
Web : http://www.easysync.co.uk
E-Mail: sales@easysync.co.uk
Prices shown exclude carriage and VAT where applicable
7
INFO & MARKET
MAILBOX
Retronics
on multimeters (3)
Dear Sir — I enjoyed very
much Jan Buiting's article on
analogue multimeters
('Retronics', December 2005,
Ed.). I myself own an excel-
lent BBC Goerz Unigor A43
analogue multimeter that I
bought at a flea market. It
has a DC sensitivity of
100 kohms/volt and its low-
est DC current scale is 10
microAmperes.
In addition to the advantages
of analogue over digital
meters mentioned in the arti-
cle, I would like to call your
attention to another one men-
tioned by Robert A. Pease in
his book Troubleshooting
Analog Circuits. On page 1 7
he says:
"Another advantage of ana-
log meters is that they are
passive devices: They don't
inject noise into your circuit
as digital meters can — even
battery powered ones. And
they have a lot less capaci-
tance to ground".
Mr. Pease is referring to the
noise generated inside digital
meters by the A/D conver-
sion process, of course.
Congratulations Jan for your
interesting article.
Carlos Urbina Pacheco
(Mexico)
Thanks for the compliment Car-
los , as they say "it makes a wel-
come change from being at the
wrong end of the customer com-
plaints line". The photograph
shows an Unigor 4S meter from
my collection.
JWWUft \7~7
\/
vl £.r L A7Vfi
Vtvp.'T T
TT
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Battery backup for bike
— help please
(Mailbox December 2005
issue refers, Ed.)
Dear Editor — I have got my
dynamo backup circuit to
work: a voltage doubling rec-
tifier solved the problem
caused by the half-wave recti-
fier's series capacitor.
I enclose the corrected
schematic. Note that the DC
isolator capacitors are mount-
ed separately beside the
dynamo, whereas the circuit
is mounted at the other end
of the bike (near the battery
pouch).
The battery is also used for
extra lamp(s) such as a turn
indicator.
The circuit seems to take
3 mA from battery when
switched over to dynamo but
even if that's just noise
picked up by the meter, I can
live with it.
I found the free Linear
Technology LTSpice program
very useful.
An alternative circuit (simulat-
ed with LTSpice) replaced the
optoisolator and BJT with a
logic-level p-channel MOSFET
(protected by a zener), and
connected battery ground to
dynamo ground.
Unfortunately, Maplin no
longer sell p-type MOSFETs so
I could not build this circuit.
I have also enclosed a photo
of the finished unit. The han-
dlebar bracket is a Minoura
battery lamp extension (long)
minus the lamp tube.
Alan Bradley (UK)
That's a happy ending then Alan ,
congratulations on getting your
circuit to work. We also thank
those readers who have written
with suggestions to help Alan find
(and solve) the problem. He also
informed us that he has further
information available on the
migration of the circuit to FETs.
Hexadokus
While compiling this month's
Mailbox pages , we're inundated
with solutions to our first and
second ' Hexadoku ' puzzles
published in the January I
and February 2006 issue. I
Apparently we succeeded I
in adding a lighter note to I
high-brow electronics stuff I
that normally fills our I
pages. We were both I
pleased and surprised to I
see that a good number I
of correct solutions I
were sent by family I
members of our read- I
ers. A number of I
solutions reached us I
by regular post I
(thank you all for I
using our new I
address). Readers
were also quick to
spot that our Hexadokus can be
downloaded free of charge from
our website. Here's some com-
ment we got from you:
"A great opportunity for us
lesser gods in electronics to
win a prize".
"Can we have a microcon-
troller version of it please."
"Took me two days to solve
but I think I have the solution."
"What a wonderful idea this
Flexadoku; just what I would
expect from Elektor."
"I just love Sudokus and was
hooked the moment my hus-
band showed your hexadeci-
mal variety. It's addictive and
crazing. And tough, too."
"The normal 9x9 Sudoku was
starting to bore me. Your hex
variety got my grey matter
milling over numbers again."
"A great puzzle. I was
already hooked on Sudokus
but yours is even worse!"
"Cost me one pencil and a
rubber to solve;
8
elektor electronics - 3/2006
i Rejektor
■ A power-wise server
ADSL, wideband and fast
cable Internet connections
spreading very fast across
countries in the world,
many of you may start to
I think about using an old
I PC as a server.
I Unfortunately many forget
I the server's additional
I power consumption adding
considerably to the electric-
ity bill. The average con-
sumption of a Pentium 1 33
. PC without a CRT monitor
is between 50 and 100
I watts. A Pentium P2-266
I consumes even 25% more!
I A typical CRT monitor will
I consume 80 watts on aver-
I age. Money-wise that's
I about 60 pounds per year
if the equipment is left on
all the time.
Mr Jeroen Baars from the
Netherlands sent us his
suggestions for reduced
I power consumption for
I small network servers,
I based on his own experi-
I ence with a Pentium 1 33
I PC. The best candidates for
this kind of server applica-
tions are PCs with a CPU
running at anywhere
! between 90 and 233 MHz
and having a Socket-7 type
motherboard. Although a
I Socket-5 or a 486
I DX/DX2/DX4 may also be
I suitable, these machines
I will be found to be sluggish
I and have somewhat higher
I power consumption.
To begin with you should
® check if the PC is still fully
functional. Run a thorough
test on the hard disk, then
make sure it's virus-free.
■ Make notes of the hard-
Under this heading we will occasionally publish circuits, ideas and
suggestions that did not make it to full publication in this magazine for various reasons (like lack of space).
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ware address and IRQ of the
network card. Next you can
disassemble the PC to pre-
pare it for its future function.
Open up the power supply
and remove dust and dirt
with a small brush. Watch
out for residual charge of the
electrolytic capacitors.
Connect the fan to 5 V
instead of 1 2 V and check it
runs smoothly and reliably on
the lower voltage. If not,
replace it by one that does.
Replace the CPU cooler by a
version without a fan. In most
cases the fan can be
removed from the heatsink
and the cooling will still be
sufficient. Replace a high-per-
formance video card you
may come across by a stan-
dard card with just 1 , 2 or 4
Mbytes of memory. If an ISA
card is used, make sure the
hardware address and IRQs
are known (for the software
installation). A PCI card will
usually stand a higher
chance of success provided it
is from a reputed supplier. A
sound card is not required. A
floppy disk or IDE card is
only necessary with a 486
machine. The available mem-
ory should be 16 Megabytes
or more.
Once everything looks fine
so far, a cheap energy meter
(£15-20 from builders mar-
kets) and the following meas-
ures will tell you how much
energy is saved.
To start with, relocate the
CPU speed jumpers to select
a setting of about 75 MHz.
With some motherboards
and CPUs, even lower
speeds may be set up.
Although apparently even
more energy-wise, in practice
you'll find that 25 to 30 MHz
is the minimum you can get
away with. In most cases
however, you'll find that "the
slower the more economi-
cal". There are exceptions
however. When testing a
stripped-down 486DX
machine no difference was
noticed when the clock speed
was reduced from 50 down
to 25 MHz. You may also
want to experiment a little
with the CPU core voltage
jumpers, making sure you
never select a voltage higher
than the original setting. If
you happen to have a small
stock of video, network and
(if applicable) HD/floppy
disk cards, it's very well
worth the time and effort to
swap these around for a
bit as one card may con-
sume far more power than
the other.
If you assemble the PC
without the help of an ener-
gy meter, be sure to use a
PCI video card.
After all this modding
around, the PC will typical-
ly consume 25 to 30 watts.
Of course, there will be
exceptions and tough cases
but then these are easily
recognised from boiling hot
chips and ditto heatsinks.
In principle, a floppy disk
is sufficient for a small web-
site, router or printer serv-
er. You will need a hard
disk however if want to run
a large website with photos
on it and FTP access. The
hard disk may, of course,
be replaced with an IDE
Flash drive: very power-
wise, quiet and perfectly
working!
The BIOS settings will usu-
ally require some changes.
The BIOS will be specific to
the motherboard used, so
some research will be
needed to find and under-
stand the settings that mat-
ter. Enable the 'halt on
errors' option in the
Standard CMOS Setup
menu. Then go to the
Power Management menu
and change the settings to
those indicated in the
screendump. Next, click on
'Save & Exit'. At that point
you are ready to proceed
with the installation of an
operating system, for exam-
ple, Freedos or Freesco.
Both have a "dot org
web address.
next one, please!"
"Took a bit longer than the
decimal ones!"
"Nice puzzle; blood, sweat
and beer!"
"Could not put it down and
got off the wrong subway sta-
tion."
"A most enjoyable distrac-
tion, I will look forward to
more of these puzzles in the
future."
Visual Basic Course
Dear Elektor people — I was
thrilled to see the free Visual
Basic course booklet with the
January 2006 issue. A fan-
tastic initiative, thank you Mr
Petros Kronis and Elektor for
your efforts!
When I wanted to download
Visual Basic Express edition
2005 I got a message saying
the product required
Windows 2000.
Unfortunately, my PC has
Windows 98. Does this
mean I am unable to pro-
ceed? I was unable to find a
'minimum requirements' list in
your booklet.
Jose Qvik (Netherlands)
The big advantage of the latest
version of Visual Basic is that it's
free. Most programs discussed in
the booklet will also run using
older versions of Visual Basic , but
these , alas , are not free. Maybe
you should start looking for an
older VB version someone is will-
ing to sell at a low price.
PIC programming
Dear Editor and lab staff — I
am looking for a handbook
3/2006 - elektor electronics
9
INFO & MARKET
MAILBOX
Corrections & Updates
SC Analyser 2005
April 2005, p. 34, 030451-1
Several readers have reported difficulties with the configura-
tion bits to set up in the PIC. The confusion is owing to poor-
ly defined standards at Microchip. Because all status bits
are at 7 1 7 with a new processor, there are options where '1 '
means 'enabled', while for other options it means 'dis-
abled'. To add to the confusion, some programmer systems
(including the one currently in use at Elektor labs) employ
the notation 'on' and 'off'.
The essential options are the oscillator, watchdog timer, low-
voltage programming and in-circuit debugger. The following
list provides the desired state for each option, where '0' =
unprogrammed and '1' = programmed.
Options:
bit 13, CP:
bit 1 1, DEBUG:
bit 10-9, WRT1 :
bit 8, CPD:
bit 7, LVP:
bit 6, BOREN:
bit 3, PWRTEN:
bit 2, WDTEN:
bit 1-0, FOSC1 :
Flash Program Memory Code Protection
bit; 1
In-Circuit Debugger Mode bit; 1
WRTO Flash Program Memory Write
Enable bits; 1 1
Data EEPROM Memory Code Protection
bit; 1
Low-Voltage (Single-Supply) In-Circuit
Serial Programming Enable bit; 1
Brown-out Reset Enable bit; 1
Power-up Timer Enable bit; 0
Watchdog Timer Enable bit; 0
FOSCO: Oscillator Selection bits; 1 1
DDS RF Signal Generator
October 2003, p. 1 4, 020299- 1
Pin 6 of IC3 is erroneously connected to the +9 V supply
rail. The relevant 1C input is however designed to handle
logic levels with a maximum High level of +5 V. Although
the 1C will not take damage from the +9 V level applied, it
is recommended to cut the relevant connection and wire
pin 6 to the +5 V supply rail.
or a course covering PIC
microcontroller programming.
Several questions in forums
failed to produce relevant
answers, so I am now turning
directly to you. Do you have
any relevant books?
Chris (UK)
All books we have available are
faithfully listed on our website ,
see SHOP — > Books & CD-ROMs.
Unfortunately there's not yet a
book that matches your exact
requirements. However ; we found
one on the Internet at
www.mikroelektronika. co.yu/
english/ product/books/
PICbook/ picbook.htm
and a series of tutorials at
www. mstracey. btinternet. co. uk/
pictutorial/picmain.htm
MSC1210
programming tweak
Dear Editor — I am happy
to report further progress
with my Elektor MS C 1210
microcontroller system
( Precision Measurement
Central, July August 2003
and Micro Webserver,
July/August 2004, Ed.). I
happened to discover that
replacing the instruction
printf("%f ....) somewhere in
the program by printf("%u
....) reduces the amount of
code generated by about
20%. Apparently, floating
point output is very byte con-
suming. The 20% extra
space I gained in this way
allowed me to extend the
program to my personal
requirements.
Patrick (Belgium)
Thanks for letting us know Patrick ,
I'm sure other MSC1210 users
will find this useful information.
Four steps
to LEDs on the mains
Dear Jan — I really liked the
extra-large instalment of
Design Tips in the January
2006 issue. Unfortunately, in
a number of cases the com-
ponent references in the texts
with Four Steps to LEDs on
the Mains are not consistent
with the schematics you have
printed. I'm happy to say that
despite the discrepancies I
did not have problems under-
standing the operation of the
circuits. Many thanks for an
interesting article.
Walther (UK)
Unfortunately the component num-
bering in the drawings was
changed from the author's hand
drawn originals we used to pro-
duce the texts. Also , LED D10 in the
third drawing is shown the wrong
way around. Given the simplicity
of the circuits discussed we trust the
errors do not detract too much
from the educational value.
MailBox Terms
- Publication of reader’s correspon-
dence is at the discretion
of the Editor.
- Viewpoints expressed by corres-
pondents are not necessarily
those of the Editor or Publisher.
- Correspondence may be
translated or edited for length,
clarity and style.
- When replying to Mailbox
correspondence,
please quote Issue number.
- Please send your MailBox
correspondence to:
editor@elektor-electronics.co.uk or
Elektor Electronics, The Editor,
1000 Great West Road,
Brentford TW8 9HH, England.
10
elektor electronics - 3/2006
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■ Alt ID lines available tor expansion
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Tel: 0845 226 9451
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INFO & MARKET
NEWS & NEW PRODUCTS
British computing power helps bring Were-Rabbit to life
Sight Systems has helped bring
the latest Aardman Animations
film, "Wallace & Gromit: The
Curse of the Were-Rabbit", to the
screen with their high-tech cus-
tom computer systems. Sight Sys-
tems helped build a custom-
developed computer called the
Aardcase that helped Nick Park
and his team to speed up the
process of bringing the plasticine
hero's, Wallace and Gromit, to
life as well as creating the huge,
mysterious veg-ravaging beast:
the Were-Rabbit!
The Aardcase is connected to
the film cameras, capturing the
images from up to 30 cameras
directly to hard disc. It allows the
animators to check the minute
changes made from one frame
the next in real time. Although
many people assume that the
technology behind blockbuster
movies is associated with large
Hollywood companies, Sight
Systems has provided some tech-
nology for several productions,
including the last Aardman film,
"Chicken Run".
The Aardcase is a single board
based PC with a passive back-
plane in a ruggedised 61) 19"
rack mount case. Aardman
demanded a highly robust prod-
uct that could be easily trans-
ported - including being
wheeled over the cobbled paths
near their office - so Sight Sys-
tems designed a custom vibra-
tion-resistant solution to ensure
that the computer would stand
up to this rough treatment. The
system includes a video capture
PCI card, an optical drive for
storing captured film, and two
hard drives. The two drives sep-
arate the video, which is stored
on a high-performance SCSI
drive, from the operating system
and software that is held on a
cost-effective ATA drive.
The custom case routes the video
connections and other I/O to a
rear panel designed for use by
animators with little or no knowl-
edge of PCs. In addition to the
video inputs, the system also pro-
vides a 1 2V supply to power the
cameras. Installed software
includes the Perception Video
Recorder from DPS as well as a
custom Video Assist and Digital
Video Frame store developed by
Aardman that helps the anima-
tors plan character movements
on screen, and allows them to
check the frame currently being
shot with those already com-
pleted to ensure continuity.
"We have provided many sys-
tems for the film and broadcast
industry, which is only one of the
applications that use our prod-
ucts," said Phil Walters, MD of
Sight Systems. "Our long rela-
tionship with Aardman shows
that we can meet the needs of
the most demanding customers
over an extended period of
time.
Wallace & Gromit: The Curse of
the Were-Rabbit is showing now
at local cinemas, featuring the
voices of Helena Bonham-Carter
and Ralph Fiennes as well as
Peter Sallis, who has been the
voice of Wallace since the first
short.
More information is available at
www.sightsystems.co.uk.
( 065079 - 4 )
In-vehicle video recorder
Reliance Motor Services (RMS)
has announced their success
with deView's Mobile Digital
Video Recorder System (DV-M8),
manufactured by Security Man-
ufacturing Limited (SML).
Reliance Motor Services are
renowned for their success and
are the 2005 winners of the
"Bus Operator of the Year"
award at the RouteONE Excel-
lence Awards." due to their qual-
ity and commitment to their cus-
tomers and staff. RMS operates
throughout the Vale of York. RMS
contacted Sewell of Leeds nearly
6 months ago to find out what
would best suit their require-
ments for CCTV for double deck
buses, which were being added
to their fleet. Sewell of Leeds
arranged to demonstrate the
deView DV-M8 and gave them
the option of a range of deView
cameras and driver screens to
meet their needs.
The DV-M8 can be installed into
any vehicle type and you can
choose what you require to view
internally or externally on the
vehicle. Camera installation is
quick with well-designed camera
mounting making set up quick
and simple. The DV-M8 system is
easy to add or integrate options
such as reversing camera sys-
tems, as well as being compact
and having the ability to bolt
directly to the vehicle without
compromising reliability makes
installation a breeze.
Full details of all deView prod-
ucts can be found on their web-
site at www.deview.com and for
more information regarding the
DV-M8, please contact Gerry
Burns, Special Project Sales.
( 065079 - 6 )
12
elektor electronics - 3/2006
FPGA-based mobile applications board
QuickLogic Europe has released
a low-power FPGA development
tool for Intel's PXA27x based
Processor Developer's Kit - the
'Mainstone' DVK - enabling
rapid adoption of emerging tech-
nologies that are not natively sup-
ported. The new Mobile Appli-
cation Board (MAB) can provide
seamless connectivity between
XScale processors and periph-
eral interfaces such as Mini PCI,
CardBus, SDIO and IDE.
QuickLogic's FPGA-based MAB
enables the development and
performance verification of
design ideas for a variety of
peripheral interfaces such as Wi-
Fi, HDD (Hard Disk Drive),
10/1 00/1 G Ethernet, MPEG
devices, SD memory, and many
more. It connects directly into
the VLIO connector of the DVK,
which allows designers to make
system measurements and archi-
tecture trade-offs including
power consumption, perform-
ance and cost.
MAB allows electronic design
teams start software develop-
ment prior to receiving final
hardware. This ability to design
hardware and software in paral-
lel can provide product develop-
ers with a critical competitive
advantage, by significantly
reducing time spent in develop-
ment of popular portable prod-
ucts such as GPS, smart phones,
portable media players, and
portable industrial systems.
The QuickLogic Mobile Applica-
M1TACHI
mad pftvi
■mm
W TT*
Travetatar
QutfXLQChC
QuicxLogic
XScale Mobile A.B
ft? V 10 ilJIOL Ik CANADA
<£> rPH
MirtJ PCI
( r r i
r
fit i ?
i it t i Hit 1 i
tion Board is available immedi-
ately. Complete solution packs
are available for both Wi-Fi and
HDD connectivity. They include
the Mobile Application Board,
an Eclipse II QL8325 device in
a 484-ball BGA package, refer-
ence design files and software
drivers for Windows CE, Win-
dows Mobile, and Linux.
In addition to this solution for
QuickLogic's Eclipse II family of
FPGAs, the company will release
a MAB based on PolarPro, the
new ultra low power FPGA, at
the end of Q1 , 2006.
For more information, access:
www.quicklogic.com/mab
QuickLogic Europe,
1 5 London Street,
Chertsey KT16 8AP,UK.
Tel. +44 1932 579011.
www.quicklogic.com
(065079-5)
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13
INFO & MARKET
NEWS & NEW PRODUCTS
Three-phase PWM controller
International Rectifier announced
a three-phase PWM control 1C
with integrated drivers for DC-
DC converters. The IR3094MPbF
enables up to 40% circuit size
reduction when used with Inter-
national Rectifier DirectFET™
MOSFETs. The smaller footprint
makes the IR3094 ideal for
space-constrained applications
like DDR memory in rack servers
and point-of-load (POL) modules
used in high-density data sys-
tems.
A typical 80A, three-phase syn-
chronous buck solution would
require as many as 13 devices
including one control and three
drivers in addition to three MOS-
FETs per phase. A chip set made
with the IR3094 plus IRF6637
and IRF6678 DirectFET MOS-
FETs reduces the silicon compo-
nent count to seven devices for
the same output current. Three
pairs of these DirectFET MOS-
FETs can be placed directly next
to the IR3094, creating a solu-
tion that minimizes printed circuit
board trace parasitics and
enables optimum switching per-
formance.
The IR3094 is designed for
applications requiring a 0.85 V
to 5.1 V output. The new 1C is
housed in a compact 7mm x
7mm MLPQ package, and fea-
tures 3A gate drive capability, a
1% accurate reference voltage,
adaptive voltage positioning and
programmable switching fre-
quency up to 540kHz. The
IR3094 provides system protec-
tion with programmable soft
start, hiccup over-current protec-
tion, over-voltage protection, and
a "power good" indicator.
The IRF6678, an ideal synchro-
nous MOSFET, features a very
low typical device on-resistance
of 1.7mOhm at 10VGS and
2.3mOhm at 4.5VGS. The
IRF6637 is best suited as a con-
trol MOSFET, with very low
Miller charge of only 4nC and
typical device on-resistance of
5.7 mOhm at 1 OVGS and
8.2mOhm at 4.5VGS. Both
MOSFETs are housed in the
medium can DirectFET package,
occupying the same board area
as a SO-8 with only a 0.7mm
profile, and improved thermal
performance through double-
sided cooling.
www.irf.com
( 065079 - 3 )
LPKF ProtoMat S42 PCB Plotter
LPKF Laser & Electronics AG
presents the LPKF ProtoMat®
S42 circuit board plotter, a new
entry-level circuit board plotter
for in-house rapid PCB prototyp-
ing. This compact system pro-
vides precision and performance
for quickly and easily milling
and drilling single-sided and
double-sided circuit board proto-
types in a single day.
The LPKF ProtoMat® S42 is an
excellent tool for colleges and
technical institutions, allowing
students and instructors to pro-
duce printed circuit boards that
are production quality and
chemical free, immediately in the
classroom environment. Low con-
sumable costs, instant turn-
around, and no need for exter-
nal vendors encourages more
practical exercises and experi-
ments in the classroom or labo-
ratory.
The ProtoMat® S42's 42,000
RPM spindle motor makes it an
excellent entry-level performer
for producing quality PCBs in-
house. Easy handling can be
increased with the addi-
tion of an optional
recognition camera, as
well as a vacuum table.
LPKF Laser & Electronics
AG, Osteriede 7,
D-30827 Garbsen,
Germany.
Tel.: +49 (0)5131-
7095-324,
Fax: +49 (0)5131-
7095-90.
www.lpkf.de
( 065079 - 1 )
14
elektor electronics - 3/2006
PC Oscilloscopes <& Analyzers
Analog + Digital
100MHz Digital Oscilloscope
Dual Channel Digital Scope using
industry standard BNC probes or analog
inputs on the POD.
40MS/s Logic Analyzer
8 logic, External Trigger and special
purpose inputs to capture digital
signals down to 25nS.
Mixed Signal Oscilloscope
True MSO to capture analog waveforms
time-aligned with logic using sophisticated
cross-triggering on any input.
Real-Time Spectrum Analyzer
See spectra and waveforms in
real-time displayed simultaneously
Waveform Generator
Load up to 128K arbitrary waveform and
replay via BNC B. Capture circuit response
simultaneously on BNC A
Get the full picture with BitScope
Mixed Signal Oscilloscopes
Turn your PC into a powerful Digital Storage Oscilloscope!
See inside your circuit with simultaneous analog, logic and spectrum
displays to make tracking down those elusive real-time bugs much easier.
BitScope combines a high speed synchronized storage scope and logic
analyzer with a programmable waveform generator and spectrum analyzer.
With "Smart POD" connected active probes and multiple software options
you've got the perfect low cost high performance test and debug solution!
U; (
- w
r . V
0* w v
o
Standard 1 M/20pF BNC Inputs
200uV-20V/div with xl 0 probe
S/W select AC/DC coupling
Switchable 50ohm termination
Arbitrary Waveform Generator
BitScope Smart POD probe connector
8 logic channels, cross-triggering
Dual channel analog inputs
Async serial I/O for external control
Supports active probes
USB 2.0 or Ethernet Connectivity
Single cable to PC or switch
Compressed data transmission
Ethernet option uses UDP/IP
Internet addressable device
Expandable and Programmable
Simple ASCII Protocol
BitScope Scripting Language
Add active probes and devices
Supplies up to 500mA via POD
BitScope and your PC provide an array of Virtual Instruments
■r • dp
\ J
BitScope DSO software for Windows and Linux
BitScope's integrated design uses standard oscilloscope probes and
a growing range of custom probes to provide functionality equal to
instruments many times the price.
BitScope plugs into third party software tools and has an open API
for user programming and custom data acquisition.
www. bitscope . com
3/2006 - elektor electronics
15
HANDS-ON
FPGA MODULE
Modern technology
for everyone
Paul Goossens
FPGAs have established a
firm position in the modern
electronics designer's
toolkit. Until recently, these
'super components' were
practically reserved for
specialists in high-tech
companies. That's all
changed now thanks to
low component prices
and free design software,
so it's high time to devote
attention to this technology
in Elektor Electronics. The
FPGA module discussed in
this article forms the core
of various upcoming
projects in the magazine.
16
elektor electronics - 3/2006
If you want to use an FPGA in your
design, there are several things you
can’t do without, including a program-
ming interface and configuration mem-
ory. We thought it would be a good
idea to incorporate the standard items
normally associated with an FPGA into
a single electronics module, in order to
avoid the need for everyone to reinvent
the wheel each time. This module can
then be used as a ‘digital core’ for var-
ious circuits. A major benefit of this
approach is that it allows
designers to concentrate
on specific applica-
tions without
having to
worry about
the sound-
ness of the
FPGA element.
Getting started is
the hard part
For those of you who
haven’t used FPGAs before,
this module and the associ-
ated prototyping board
described elsewhere in this issue
form an ideal starting point for
learning about FPGAs.
It’s impossible to avoid using SMDs in
a circuit such as this. To make things
even worse, we decided to use an
FPGA in a BGA package for this cir-
cuit, which means DIY soldering with
a normal soldering iron is simply
impossible. Soldering the other mem-
ber of the family (in a PQFP package)
is also very difficult. However, using
these ‘difficult’ components allows the
overall dimensions of the circuit board
to be kept reasonably compact.
Fortunately, you don’t have to worry
about assembling the board, because
the FPGA module is available from
Elektor Electronics with most of the
components pre-assembled. The only
components you have to solder by
hand are the connectors.
Besides this module, you will need a
programming interface that sits
between the PC and the FPGA board.
Naturally, we’ve also developed a
design for this interface.
Technical features
• Altera Cyclone FPGA
• 1 2,060 logic elements
• 4 MB configuration memory
• 8 MB user SRAM
• 1 MB user flash RAM
• on-board 50-MHz clock
• JTAG/programming interface
• Byteblaster compatible
• 80 user I/O lines
• dedicated clock signals
• indicator LED
• built-in switch-mode power supply
• small multilayer PCB (1 10 x 77 mm)
• supplied ready to use
It takes more than just an FPGA
to make a circuit
As already mentioned, you’ll need
some peripheral electronics to enable
you to use an FPGA in a practical cir-
cuit. One of the most important ele-
ments beside the FPGA is the configu-
ration memory. In contrast to most
FPGAs, the configuration memory
retains its data when the supply volt-
age is switched off.
Each time the unit is switched on, the
FPGA must be configured again before
it can fulfil its intended function. Fortu-
nately, FPGA manufacturers have
developed special memory ICs that
can configure FPGA ICs automatically
when power is switched on. Our cir-
cuit includes one of these memory ICs.
Easy programming of the FPGA and
the configuration memory during the
development phase is also highly
desirable. That’s why a programming
interface (using JTAG) also forms part
of the standard peripheral circuitry.
Another quite important part of such a
circuit is the power supply. The inter-
nal operating voltage of most such ICs
is quite low (1.5 V in our case). The
power supply must be able to handle
short current spikes without problems.
In addition, a different voltage is used
for the inputs and outputs. Here we
decided to use 3.3 V. The supply for
this voltage must also be able to
deliver fairly heavy currents and
remain stable under heavy loads.
Our circuit also includes an oscillator,
SRAM and flash memory. They can be
used freely by the application.
All the individual elements of the cir-
cuit can be easily identified in the
schematic drawing.
The design
Due to the size of the schematic draw-
ing of the FPGA module, we decided to
print it on a foldout which may be
found in the centre of the magazine.
Let’s start at the beginning with the
power supply. It is built around a
TPS75003 (IC2) and can work with an
input voltage in the range of 4. 5-6. 5 V.
This IC is specially designed for use in
FPGA circuits. It contains two switch-
mode power supply circuits and one
series regulator. The latter is not used
in our circuit; only the two switch-
mode circuits are used.
A step-down regulator that provides a
3.3-V supply voltage is implemented
using Tl, Dl, LI, Cl and associated
components. IC2 periodically drives
FET Tl into conduction to allow a cur-
rent to flow from the input voltage via
Tl, LI and Cl. This causes the current
through the inductor to increase,
which in turn causes capacitor Cl to
be charged. When IC2 switches off the
FET, the current flowing in LI cannot
stop immediately, so it continues to
flow through Cl and Dl. Rl, R3 and C3
provide feedback so IC2 can determine
whether it has to supply more power
or less power.
The values of these components have
been chosen such that IC2 tries to
maintain the output voltage at 3.3 V.
Resistor R2 is a sense resistor. IC2 will
limit the current if the voltage across
3/2006 - elektor electronics
17
HANDS-ON
FPGA MODULE
Figure 1. The programming mode of the Quartus program.
this resistor rises above 0.1 V. The
value used here (50 mil) results in a
current limit threshold of 2 A.
A similar circuit is built around T2,
with only the values of the feedback
resistors being different. They are cho-
sen to yield an output voltage of 1.5 V.
The electrolytic capacitors at the input
buffer the input voltage. They also pre-
vent fast current spikes from leaving
the board. That prevents generation of
interference that could impair the oper-
ation of nearby equipment.
The FPGA is powered from these sup-
ply voltages, but not directly. The sup-
ply lines for the two sections of the
FPGA are first fed through ferrite
beads to block high-frequency radia-
tion. The supply voltages are also
buffered close to the IC by several
additional capacitors. That may appear
to be a bit of overkill, but fairly large
switching currents at high frequencies
can flow through the FPGA, depending
on the final circuit configuration. It is
always a good idea to keep the paths
of such currents as short as possible.
Otherwise the circuit can easily gener-
ate too much undesirable interference.
And now for the digital part
Now that we’ve looked after the sup-
ply voltages, we can turn to the digital
portion of the circuit. The first thing the
FPGA needs is a configuration mem-
ory. That memory is present in the cir-
cuit in the form of IC6, which has been
designed to work with the FPGA.
When the MSEL signals from the
FPGA are at ground level, the IC
expects to find a configuration memory
(such as the EPCDS4) connected to it.
The FPGA will then independently
control the memory IC and read data
from it in order to configure itself based
on the data. That makes the process
very easy in actual use.
A programming connector (K5) is pro-
vided for programming IC6. The pin
assignments of this connector have
been chosen to make it compatible
with the Altera ‘Byteblaster’ program-
ming interface.
Connector K6 is used for in-circuit pro-
gramming of the FPGA from a PC. That
makes it unnecessary to first program a
design into the configuration memory.
This connector can be used to quickly
test a design without using the config-
uration memory.
Here again, the sig-
nals are arranged
to be compatible
with the Byte-
blaster interface.
The circuitry
around T3-T5
forms an indicator
circuit that clearly
displays the status
of the FPGA using
bicolour LED D3.
Any error states
that may occur are
also indicate visibly
by D3.
An abundance
of I/O
As this circuit is
intended to be
used for all sorts of
applications, it has
an abundance of
I/O pins. They are
accessible via con-
nectors K3, K4, K7,
K8 and K2. These
connectors fit stan-
dard pin headers
with 0.1” pin spac-
ing. That avoids
the difficulties of using SMD connec-
tors on the motherboard and thus
makes it quite easy to connect the
board to your own hardware.
Connectors K3, K4, K7 and K8 present
an impressive total of 80 I/O pins of the
FPGA to the outside world. The I/O
lines are all routed to one side of each
connector. The supply voltage (3.3 V)
and ground are available on the other
side on alternating pins. You can use
the supply and ground pins to power
your own circuit if it doesn’t require too
much current. This supply voltage is
also filtered on the module by a ferrite
bead and two capacitors.
Connector K2 provides a special con-
nection. Besides ground lines, it has
several signals that are specifically
intended to be used as clock signals.
Pin 10 is an input that can be used to
supply an external clock signal to the
FPGA. The remaining even-numbered
pins are all connected to the outputs of
the internal PLLs of the FPGA.
Of course, it’s possible to provide an
external clock signal on any other
desired input of the FPGA, but these
pins are specifically intended to be
used for that purpose.
18
elektor electronics - 3/2006
The extras
Many FPGA-based designs require
memory. Although there is memory
available in the FPGA, it’s not enough
for many types of applications. In light
of the fact that a ‘softcore’ processor is
often used, a flash memory can be
quite handy for storing the firmware of
the processor. That makes it possible
to use larger amounts of code in appli-
cation designs without taking up addi-
tional space in the FPGA. The flash
memory takes the form of IC5 in the
schematic diagram.
A bit of extra RAM can also be desir-
able in some cases. Besides being use-
ful if one or more softcore processors
are used in the FPGA, additional RAM
can also be welcome for various types
of signal processing.
The RAM memory is provided by IC3
and IC4. These ICs have a capacity of
4 Mbits and are configured as 256K 16-
bit words. Signals BHE and BLE can be
used as two separate CE lines, with
BHE being the chip-enable line for the
upper byte (D8-D15) of the data lines
and BLE the chip-enable line for the
lower byte (D0-D7). That means this
memory can also be used as a 512-KB
memory with 8-bit data.
IC3 is connected directly to the FPGA,
while IC4 shares its data and address
busses with the flash memory (IC5).
The busses are shared to ensure that
enough I/O pins of the FPGA are kept
free for the user connectors. However,
that means the FPGA cannot read or
write the RAM and flash memory at
the same time. That doesn’t form a
major problem in practice, especially
when softcore processors are used.
That completes the description of the
main parts of the circuit.
We already mentioned that the circuit
board for the module is provided nearly
fully assembled. The only thing you
have to do is to solder the eight pro-
vided connectors to the board. Connec-
tors K2, I<3, K4, K7 and K8 are fitted on
the bottom of the board. The other
three connectors are fitted on the top
of the board (on the component side).
Make sure pin 1 of each connecter is in
the right position, which is marked by
a ‘1’ on the component overlay.
Programming interface
This module by itself is only a starting
point. The FPGA and/or configuration
memory must be programmed before
they can be used. That requires a pro-
gramming interface. The schematic
diagram of the programming interface
is also shown on the foldout. It con-
nects the FPGA or configuration mem-
ory to the parallel port of a PC. The
programming interface is compatible
with the Altera Byteblaster interface
and can be used with free Altera soft-
ware. The circuit is quite straightfor-
ward.
Everything is powered by 3.3 V taken
from the FPGA module. The two ICs
are used to convert the +3.3-V signals
from the FPGA to + 5-V signals for the
PC and vice versa. The 100-Q resistors
prevent the + 5-V signals from raising
the supply voltage above the allow-
able level.
The interface is connected to the par-
allel port of a PC via connector K3. K2 is
a box header that is connected to the
FPGA board by a 10-way flat cable
with a matching plug at each end.
If you just want to program the FPGA
in order to test something, this cable
must be connected to K6 ( JTAG) on the
FPGA module. If you want to program
the module so it can operate on its
own, this cable must be connected to
K5 (PROGRAM) on the FPGA module.
Software
A project of this sort naturally includes
corresponding software. The manufac-
turer of the FPGA we use here, Altera,
has a very nice package of support
software for its FPGAs. The free ver-
sion of the software is called ‘Quartus
Web Edition’ and can be downloaded
from the manufacturer’s website
(www.altera.com). It’s a quite sizeable
download (240 MB at the time of writ-
ing this article), but you can also
request a free CD-ROM on the Altera
website.
After installing the software, which by
the way goes without a hitch, you will
need a licence. You can also obtain this
via the Altera website, and it is valid
for six months. At the end of the six
months you can request a new licence.
For the sceptics among our readers,
the manufacturer has assured us that
this software will remain free in the
future.
There’s not enough room here to show
you everything you can do with this
software, and it’s equally impossible to
present a full course in VHDL here. If
you’re new to using FPGAs, you
should have a look at the accompany-
ing FPGA Prototyping Board described
elsewhere in this issue.
Testing
Although this circuit does not have
any real input or output capabilities,
it’s still possible to make a simple
test.
After installing the software, it’s
best to switch off your PC for the
next steps. Start by connecting the
programming interface to the paral-
lel port of your PC. Next, use the
supplied 10-way flat cable to con-
nect the interface to the FPGA mod-
ule. You should connect the flat
cable to connector K6 (JTAG) on the
FPGA module. Now switch on the
PC and connect a power source to
the FPGA (caution: maximum volt-
age 6.5 V).
Start up Quartus and then click on
the programming icon in the menu
bar, or click on the Tools menu and
select Programmer (the result will
be the same in either case). The pro-
gramming window will be opened.
Click on the Hardware Setup button,
and then click on Add Hardware in
the new window. Select ‘Byte-
blaster’ and specify the printer port
you connected to the programming
interface (usually LPT1:).
If you then click on the Autodetect
button in the main window, the pro-
gram will automatically detect your
FPGA (EP1C12). That way you can
be sure the FPGA is working and
the supply voltage is present.
( 040477 - 1 )
The Versatile FPGA module can be
ordered from
Elektor Electronics Readers Services
under order number 040477-91 .
Included
items
• FPGA module (ready to use)
• programming interface (ready to
use)
• programming cable
• interconnect cable (between PC
and programming interface)
• 8 pinheaders (supplied
separately)
3/2006 - elektor electronics
19
HANDS-ON
FPGA PROTOTYPING BOARD
VGA
A genuine VGA output that you can
use to display text and imagery on a
PC monitor. It's all done with only a
few standard components.
See page 24.
Ethernet
Your link to the Internet. The associat-
ed 1C provides the coupling between
the analogue and digital portions.
See page 24.
USB
This USB interface makes communi-
cation with your PC fast and easy.
And it takes only five components,
including the connector!
See page 24.
Analogue I/O
Four analogue inputs and one ana-
logue output. In addition to all the
digital artillery on the board, an ana-
logue interface is naturally indispen-
sable. This I/O port has a resolution
of 8 bits, which is enough for most
applications.
See page 24.
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This interface allows you to connect
You can use the LEDs for a visible
your own circuitry to the
indication of the status of
prototyping board.
various components.
See page 24.
See page 24.
20
elektor electronics - 3/2006
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Power supply
The power supply is pretty tolerant.
As long as the input voltage is some-
where between 6 V and 20 V, the
regulator will take care of the rest.
You don't even have to worry about
getting the polarity right - the power
supply circuit doesn't care.
See page 25.
PS/2
A port for a PC keyboard and
mouse.
See page 25.
LCD
A two-line LCD module with a maxi-
mum of 16 characters per line. An
essential part of every proper proto-
typing board!
See page 24.
Audio I/O
With 16-bit stereo input and output,
this prototyping board can also hold
its own in the audio world.
See page 25.
Displays
The ideal way to display numbers.
Also handy for displaying the date
or time.
See page 24.
Pushbuttons
Besides all sorts of sophisticated
inputs and outputs, simple operation
using pushbuttons is often desirable.
See page 24.
DIP switches
For enabling or disabling options.
Naturally, they can also be used as
independent switches.
See page 25.
3/2006 - elektor electronics
21
HANDS-ON
FPGA PROTOTYPING BOARD
This prototyping board
provides an environment for
the FPGA module that
enables it to do something
useful. That gives you an
opportunity to discover the
capabilities of our FPGA
module for yourself.
Naturally, you don't have to
make this voyage of
discovery all on your own -
a course in the form of a
series of instalments in
upcoming issues will guide
you on your way.
We’ve designed a prototyping board
that enables the FPGA to be used for a
variety of tasks. As you can see from
the list of features at the head of the
article, it’s equipped with quite a few
modern interfaces.
For many of our readers, designing a
circuit that will ultimately be imple-
mented in an FPGA will be a totally
new experience. For that reason, we’ll
start a series of articles on FPGA pro-
gramming in next month’s issue. It will
be based on the prototyping board
described here.
Just like the FPGA module, this circuit
board is supplied in ready-to-use form.
»>
Figure 1 . Schematic diagram of the FPGA
prototyping board. The board layout is available
free of charge in PDF format at www.elektor-
electronics.co.uk.
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3/2006 - elektor electronics
23
HANDS-ON
FPGA PROTOTYPING BOARD
VGA
Our prototyping board even has its own
VGA output. The circuitry for this can be
found around K9. Three super-cheap
D/A converters are implemented using
six resistors. The synchronisation signals
can remain in digital form. As signal
reflections can be expected here, all of
these lines are protected against over-
shoots by a set of fast Schottky diodes
(D15-D19).
Generating a VGA signal is easier than
it appears. After reading the seventh
instalment of the course, you'll know
exactly how it's done.
Ethernet
The Ethernet interface is built around
IC5, which converts digital signals into
analogue signals and the other way
around, all according to the Ethernet
standard. Driving this interface is fairly
complex. In the ninth instalment,
well use this interface to perform some
experiments on a network.
7-segment
displays
The board has four 7-segment displays
with decimal points, which are housed
together with three separate LEDs in a
single package (D20). This display has
several common-anode leads (5 in total).
They can be individually connected to
the supply voltage to determine which of
the five areas of the display should be
illuminated. Here four of them are used
for the four 7-segment displays and asso-
ciated decimal points. The fifth lead pro-
vides current to the three separate LEDs.
The anode leads can be used to con-
trol which elements of these five areas
light up.
For the drive signals, we use the same
type of 1C as for the LED drive signals.
Several outputs of 1C 10 and IC1 1 are
used to switch the anodes to ground
under control of the FPGA. Five leads
are used to switch transistors T1-T5. In
this way, we can use signals
DIG1-DIG4 and DIG L to control which
part of the display is active.
Driving this display is somewhat difficult
because the various parts of the display
must be driven in rotation. We'll illus-
trate how to do this in the second
instalment of the FPGA course.
Digital I/O
We can easily imagine that the proto-
typing board will be used as a control
unit for something or other. There are
eight digital I/O lines to allow user
hardware to be connected to the proto-
typing board.
The 1C we selected for this purpose (IC4)
has an l 2 C interface. This interface is
also used to communicate with another
1C that we'll describe shortly.
The circuit around T8 and T9 has
already been used in another Elektor
Electronics design. It converts the 3.3-V
l 2 C signals into 5-V l 2 C signals.
The l 2 C bus uses a serial data transmis-
sion protocol. The way this is implement-
ed in the FPGA will be described in the
third instalment of the course.
USB
A standard USB interface is built round
connector K1 0. It can be optionally con-
figured to present itself as a fast or slow
USB device. The PC recognises a fast
USB device by the fact that the D+ USB
line is pulled up to the positive supply
voltage by a resistor. For a slow device,
the D- line of the USB is pulled to
ground by a resistor.
On the prototyping board, either option
can be selected by the FPGA as desired
by switching FETs T6 and T7 on or off.
Here again, the two data lines are wired
directly to the FPGA.
We'll perform a few experiments with
the USB bus in the eighth instalment.
Analogue I/O
Besides the digital I/O options, the
board has four analogue inputs and one
analogue output. These 8-bit I/O ports
are provided by IC3, which also has an
l 2 C interface. For that reason, this I/O
option will also be described in the
third instalment of he FPGA course.
LEDs
LEDs D8-D14 can be driven directly
from the FPGA module by signals LED 1 -
LED7. IC7 buffers the drive signals.
Whenever an input is at a logic High
level, the corresponding output is pulled
to ground. The currents through the LEDs
are limited by resistors R12-R27.
This type of drive is very simple. In the
first instalment of our FPGA course,
we will use these LEDs to study various
digital functions.
Pushbuttons
One of the input options of the proto-
typing board takes the form of pushbut-
tons. This is provided by pushbutton
switches S1-S4. Signal lines
SWITCH 1-SWITCH4 are held low by
resistors R5-R8 when the pushbuttons
are not pressed. If a pushbutton is
pressed, the associated signal line is
pulled up to the supply voltage. Signal
24
elektor electronics - 3/2006
lines SWITCH 1-SWITCH4 are con-
nected directly to the FPGA module,
just like the LED signal lines.
You can use the pushbuttons to control
the states of four signal inputs to the
FPGA. These four pushbuttons will also
be used for simple input functions in the
first instalment of the FPGA course.
DIP switches
Switch module S5 houses eight small
switches, which are wired the same way
as pushbuttons S1-S4. They allow an
additional eight signal inputs of the
FPGA to be controlled by the user.
A good application for switches of this
sort is to use them for enabling or dis-
abling various options. We will use
these DIP switches in the second
instalment of the FPGA course.
digital I/O lines.
Well put the LCD through its paces in
the fifth instalment.
PS/2
A PS/2 keyboard and mouse can be
connected via connectors K14 and K15.
Both signals on this bus are connected
directly to the I/O pins of the FPGA
module. As with most of the other I/O
ports, the FPGA provides 'intelligent'
control for these signals. Even the bidi-
rectional data signal can be processed
directly by the FPGA without the inter-
vention of any external ICs. This commu-
nication uses a special serial transmis-
sion protocol, which well examine more
closely in the sixth instalment.
The "brains" on the Versatile FPGA Unit.
Audio I/O
The circuitry around 1C 12 forms a gen-
uine 16-bit stereo input/output port. The
sampling frequency is set to 48 kHz by
the clock rate of IC1 3.
This 1C communicates with the FPGA via
five signal lines, which will be described
in more detail in the fourth instal-
ment of the course. Naturally, that will
also include an example of an applica-
tion in which the 1C is driven by the
FPGA.
LCD
The 2-line by 16-character LCD (LCD1
on the schematic diagram) is driven by
IC6 and IC8. These ICs operate on the
same principle as the ones used for the
Power supply
All of this is rounded out by the power
supply. That's the only part of the circuit
that isn't controlled by the FPGA.
IC1 and IC2 are both step-down con-
trollers. Each of these ICs forms a step-
down converter in combination with an
inductor, a diode and buffer capacitors.
The advantage of these converters is that
a high input voltage doesn't cause the
supply to dissipate a lot of power in the
form of heat, unlike a series-regulated
power supply using a 7805 or the like.
The input voltage on K1 can be con-
nected either way round. D1 and
D4-D6 sort things out so the polarity of
the voltage at the inputs of IC1 and IC2
is always correct. The electrolytic
capacitors at the input ensure that fast
switching currents stay on the board
where they belong. As a result, the
power supply generates relatively little
interference.
The FPGA is powered via K2.
( 050370 )
The Ethernet interface built around IC5.
3/2006 - elektor electronics
25
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Drives any 5, 6 or ELlead
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Supply 9Vdc, PCB. 00x50 mm
Kit Order Code 31 79KT - 1 1 1 .96
Assembled Order Code AS3179 £18.96
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Drive any bipolar stopper
motor uw rig exlemeily sup- . - *ji
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Supply 8-30Vdc. PCS: 75x6Smm
Kit Order Code 31 58KT - £ 14 .96
Assembted: Order Code AS3159 - £27,16
Most ate his are available in tall form (KT suffix)
or assembled and ready for use (AS prefix),
CREDIT CARD
SALES
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Cofrlroileri A Loggers
Here are just a few of the controller and
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Sec website ter full details Suitable PSU
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Rolling Code 4 -Channel UMF Remote
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Compute! Temp erai u re Data Logger
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Continuously lo gs up to 4
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Computer puntroiitd 6-
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Power Supply: OVdc-EOOmA
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Infrared R C Relay Board
Individually control 12 on-
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Toggle or mome-nta ry 1 5m *
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Progt&mmw Ac eMtflr/ 4 |?
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Leads: Parallel (LDC 136) £4 96 t Serial
(LDC441) £4.96 / USB (LPC944} £2 J6
mm* USB All-Flash PIC ProgmfnmaL
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Krt Order Code 312SKT-E34J6
Assembled Order Coda. AS31 2fl - £44.96
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uses serial pert and any
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3/2006 - elektor electronics
27
INFO & MARKET
DEVELOPMENT KITS
In this issue, which is bursting with FPGAs and microcontrollers, they could not possibly
be omitted: development kits! We devote attention to interesting but affordable kits
where we not only look at kits that are suitable for a commercial environment but which
are also very interesting for hobby use.
The first few steps are always difficult. This is also true of
course when working with FPGAs, microcontrollers and
DSPs. Particularly in order to acquaint commercial devel-
opers in an easy way with new products, various chip
manufacturers offer so-called 'development kits' (some-
times also called 'starter kits'). But if you would like to use
them at home for yourself, then that is generally not a
problem at all. You can usually just order a kit from the
appropriate distributor for private purposes. There is then
nothing to stop you from messing about with your chosen
kit. The only catch is that you 'just' have to decide which
kit you would like to get started with. And this can be
much more involved than you would think at first glance.
In this article we attempt to give you an overview of inter-
esting and affordable kits. We selected a few kits from
each category and have summarised the important
details in a table.
Options
As already mentioned, before you start your development
effort, you have to make a choice from the different
options on offer from the various manufacturers. It is a
good idea to not just consider what you need at this par-
ticular moment, but also to think ahead about possible
extensions you may wish to add at a later date. Imple-
menting a small design in an FPGA is generally not a
problem, but a larger design (i.e., more gates) can be
more trouble to make fit. That is why development kits
are often equipped with one of the larger members, if not
the largest member, from a family. For microcontrollers
too, it is good to take into account your future require-
ments. Using fewer inputs and outputs is always possible.
Wanting to use more than the 1C provides is impossible.
Even the choice between an FPGA and a microcontroller
may not be that immediately obvious. A microcontroller is
less complex than an FPGA, but an FPGA, on the other
hand, offers many more possibilities.
The development boards have a number of inputs and
outputs for communication with other devices (that they
may potentially control). The RS232 port remains a very
familiar interface. In many cases headers are used, so
that every pin from the 1C can be accessed easily. Some
boards have a number of ADCs and DACs and occasion-
ally CAN, SPI and 1 -Wire-interfaces make an appear-
ance. For programming, each board has its own specific
connector. Microchip uses a so-called ICD programming
interface, while others use RS232, JTAG or some other
specific interface. The same holds true here: try to think
ahead of what you may need at a later stage.
In the large table we have included a number of critical
characteristics so that it becomes relatively easy for you
to make the final decision.
Nevertheless, we will provide some guidance to the start-
ing developer by describing the broad characteristics of
microcontrollers, DSPs and FPGAs.
Microcontrollers
A microcontroller is essentially a computer in one chip
(refer Figure 1). The arithmetic unit is integrated
together with all the I/O and memory in one 1C, so that
no additional chips are required (in contrast to a micro-
processor which does need additional chips). Microcon-
trollers are used mainly for controlling electronic equip-
ment, such as, for example, our recent SMD Oven (see
Elektor Electronics January 2006).
The difference between an 8-bit and 1 6-bit controller is
28
elektor electronics - 3/2006
J?CW«0CTOfl
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mainly the speed. A 1 6-bit controller can, compared to
an 8-bit controller with the same number of MIPS (Million
Instructions Per Second), process twice as much data.
Most of the demo boards have been designed in such a
way that they can function on their own. That means in
most cases that there is a microprocessor on the board
that runs a (demo) program. In addition there is then the
possibility to simu ate the board using the bundled soft-
ware and, if the program is not quite 1 00 percent cor-
rect, use debug-mode to iron out the last wrinkles.
In the text box you can read some more regarding the
choices for a particular type of microcontroller.
DSPs
DSP means Digital Signal Processor. Such a processor is
really a kind of specialised microprocessor. The signifi-
cant difference between a microcontroller and a DSP is
that a DSP has been optimised for the mathematical oper-
ations that are necessary for digital signal processing.
For example, a DSP has a special register structure and
mechanisms to carry out an FFT (Fast Fourier Transform,
a mathematical operation to analyse the frequencies in a
signal) as quickly as possible and to move large blocks
of data as efficiently as possible.
These days the boundary between DSPs and microcon-
trollers is becoming increasingly blurred, for example the
PIC series from Microchip. The microcontrollers are then
provided with the partial functionality of a DSP (which
means additional instructions).
FPGAs
An FPGA (Field Programmable Gate Array) is, as the
name implies, a 'field' with programmable logic gates
and programmable internal connections (see Figure 2).
It is a real millipede. An FPGA can be programmed so
that it carries out all kinds of logical operations. Ranging
\Z
RAM
Configurable Logic Block
FPGA
I/O Buffer
CLB
CLB
CLB
PSM
PSM
/
CLB
/
/
CLB
CLB
I/O Buffer
050324-16
Figure 1 . Block diagram for a typical microcontroller.
Figure 2. Typical architecture of an FPGA.
3/2006 - elektor electronics
29
INFO & MARKET
DEVELOPMENT KITS
Microcontrollers
Manufacturer /
Website
Type of 1C supplied
Programming
Interface
I/O
LCD
Power Supply
R.R.P.
PICDEM 2 Plus
Microchip /
www.microchip.com
PIC18F452 and PIC16F877
ICD
RS232
2x16
standard 9 V DC
adapter
£59
PICDEM 4
Microchip /
www.microchip.com
PIC12F1320 and PIC16F627A
ICD
RS232; PIC16LF72 I/O expander
2x16
standard 9 V DC
adapter; 9V battery
£76
DS89C450-K00
Maxim/Dallas
Semiconductor /
www.maxim-ic.com
DS89C450
RS-232
2x RS232; 4x 8-bit I/O
-
6-9 V DC adapter
£62
Z8 Encore! XP 4K Series
Development Kit
Zilog / www.zilog.com
Z8F0XXA (selectable)
USB or serial
RS232; IrDA, header for ADC
input (up to 8 channels),
-
5 V adapter supplied
£35
Z8 Encore! MCU
Development Kit
Zilog / www.zilog.com
Z8FXX (selectable)
USB or serial
RS232, IrDA, header for ADC
input (up to 8 channels)
-
5 V adapter supplied
£35
SK-XC866 Starter Kit
Infineon /
www.infineon.com
XC866
JTAG
RS232, CAN, LIN, JTAG; Headers
for motor control and SBC board
-
8-1 8 V adapter
£100
eCOGl Development Kit
Cyan Technology Ltd /
www.cyantechnology.com
eCOGl
Parallell port
Fast Ethernet, parallel; debugger
interface; 2x RS-232; \K, SPI,
IrDA
2x16
adapter supplied
£200
AVR STK500
Atmel/ www.atmel.com
AT90S8515-8PC
RS232
2x RS-232; pin-headers for I/O
ports of any AVR
-
10-15 V DC adapter
£90
R8C Starter Kit
Elektor/Glyn / www.
elektor-electronics.co.uk;
www.glyn.com
Renesas R8C-13
R5F21 1 34FP#U0
RS232
USB; 2x serial port; LCD connnec-
tion
-
via USB or adapter
£62
DSP's
dsPICDEM 2
Microchip /
www.microchip.com
dsPI(30F401 1
ICD
RS232; CAN; headers for all I/O
ports
2x16
standard 9 V DC
adapter
£58
Explorer 1 6
Microchip /
www.microchip.com
PIC24FJ1 28GA01 0 and
dsPIC33Fl 28GP71 ODSC
ICD, JTAG and PICIcit 2
USB; RS232, JTAG; headers for
all I/O ports; PICTail Plus
2x16
9-1 5 V DC adapter
£75
MAXQ2000-KIT
Maxim/Dallas semicon-
ductor/
www.maxim-ic.com
MAXQ2000
JTAG
RS232, JTAG, 1 -Wire interface;
headers for all I/O ports
41/2
Via JTAG-interface,
5V and
6-9 V DC adapter
£55
FPGA's
High Volume Starter Kit
Bundle (comprising
Spartan-3 Starter Kit and
CPLD Design Kit)
Xilinx/www.xilinx.com
XC3S200-4FT256C (FPGA),
XC9572XL-10VQ44C and
XC2C256-7TQ144 (oolrunner-ll
(CPLDs)
JTAG
RS232; JTAG; PS/2 mouse / key-
board port, 3x 40-pin header
-
supplied
75
MAX II Development Kit
Altera / www.altera.com
MAX II EPM1270F256C5 (CPLD)
JTAG via ByteBlaster
USB; PCI; JTAG; Altera Expansion
Prototype Headers
2x16
via USB- of PCI-bus
£105
ADDS-21 261/Cyclone
Evaluation Kit
Altera / www.altera.com
Cyclone EP1C3 (FPGA) and ADSP-
21261 (SHARC DSP chip)
JTAG for FPGA, USB for
SHARC
USB; RS232; JTAG; expansion
header
-
via adapter
£140
EasyFPGA's EZ1KUSB
Development Kit
EasyFPGA /
www.easyfpga.com
Altera ACEX EP1 K50TC1 44-3
USB or JTAG
USB; JTAG; 58 I/Os
-
via USB or supplied
6V DC adapter
£130
Morph-IC
Morph-IC/
www.morph-ic.com
Altera ACEXEP1K10TC1 00-3
USB
USB; 2x20-pin header
-
via USB or supplied
5V DC adapter
£65
30
elektor electronics - 3/2006
Devices Accepted
Manual
Software
Required for programming Miscellaneous items supplied
18-, 28,- & 40-pin PIC16XXXX
and PIC18XXXX
on CD
MPLAB IDE, MPASM, MPLAB Cl 8
PRO MATE II, MPLAB PM3, PIC-
START PLUS or MPLAB ICD 2
5k potentiometer, TC74 temperature sensor, piezo buzzer
8-, 14-,& 18-pin PIC16XXXX
and PIC18XXXX
on CD
MPLAB IDE
PRO MATE II, MPLAB PM3, PIC-
START PLUS of MPLAB ICD 2
NanoWatt technology/supercapacitor circuit, four 5k potentiometer,
space for LIN transceiver and motor driver
DS89C430, DS89C440,
DS89C450, DS5000
on CD
Microcontroller Tool Kit (MTK)
Software only; PC (MTK)
64kB Flash memory, 1 28kB SRAM
not exchangeable
on CD
ZDS II Integrated Development
Environment, ANSI C-compiler
Supplied serial or USB Smart
Cable
256-1 k bytes RAM, 1 -4k flash memory, 2 16-bit timers, comparator.
Optional: 8 channel 1 0-bits ADC, temperature sensor
not exchangeable
on CD
ZDS II Integrated Development
Environment, ANSI C-compiler
Supplied serial or USB Smart
Cable
l-64k bytes Flash/ROM, 256-4k bytes RAM, up to 60 I/Os, up to 24
interrupts, up to 4 1 6-bit timers, up to 1 2 channels 1 0-bit ADCs,
optional: DMA controller, SPI and l 2 C.
not exchangeable
on CD
Evaluation versions of Keil uVision and
Ulink or Hitex debugger Tantino-Eco,
DAvE
Tantino USB (supplied)
Compatible with 8051, PWM generator, 10-bit ADC, 3 16-bit timers,
27 general purpose I/O, 768 bytes RAM, 16k flash, potentiometer
eCOGl
on CD
CyanIDE with ANSI C-compiler, simula-
tor, debugger and Configuration Tool
Software only; PC
2MB 16-bit SDRAM, piezo buzzeer, 12-bit ADC, temperature sensor
8-, 20-, 28- and 40-pin AVR
(Attiny, AT90S, ATmega)
on CD
AVR Studio
Software only; PC
2Mbit dataflash
not exchangeable
In Elektor /
on website
KD30, NC30, HEW, Flash Development
Toolkit
Software only; PC
8-bit timer, 1 2 channel 1 0-bit ADC, 5 external & 1 1 internal inter-
rupts, 4kB flash, 1 Ok potentiometer
18-, 28- and 40-pin
dsPIC30FXXXX
on CD
MPLAB IDE
MPLAB ICD 2
potentiometer, temperature sensor, nine 1 0-bits ADC channels, SPI
PIC24 and dsPIC33 families
on CD
MPLAB IDE
MPLAB ICD 2
temperature sensor TC1047A, 10k potentiometer, 256kb EEPROM
not exchangeable
MAX-IDE
Software only; PC
MAXI 407 ADC/DAC, potentiometer, JTAG interface board, LCD board
Spartan-3, Coolrunner-ll,
XC9500XL
On paper and CD-
ROM
Evaluation versions of Xilinx ISE &
EDK
Supplied JTAG3 cable
3-bit, 8-colour VGA display port, 1MB SRAM
not exchangeable
on CD
Quartus II Web Edition
ByteBlaster II parallel download
cable
Temperature sensor, potentiometer 1 28kB SRAM, onboard power
meterr
not exchangeable
on CD
Evaluation version Visual DSP++,
Quartus II Web Version
Software only; PC
64 Mb SDRAM, 64Mb EE memory, 4Mb Flash
Altera ACEX EP1K10TC144-3,
ACEX EP1 K30TC1 44-3, ACEX
EP1 K50TC1 44-3
on CD
Quartus II Web Edition, USB-drivers
Software only; PC
not exchangeable
on CD
USB drivers, FPGA loader program,
Windows DLL (for use with Visual
C++, Visual Basic, Borland Delphi),
Quartus II Software Starter Suite
Software only; PC
Onboard 93C56 EEPROM
3/2006 - elektor electronics
31
INFO & MARKET
DEVELOPMENT KITS
from basic logic gate functions (AND, OR, XOR, NOT,
etc.) to complex combinational logic such as mathemati-
cal functions and decoders. It is even possible to emulate
a complete (8051) microprocessor in an FPGA (provided
that the FPGA has enough gates, of course).
These ports are formed by CLBs, which are connected in
a matrix arrangement. Each CLB consists of multiple
lookup tables (LUT), a few multiplexers and optionally a
number of flip-flops. So the CLBs carry out all logic func-
tions. By connecting the CLBs with programmable
switches to each other in the right way, the desired func-
tionality is obtained. The development software generally
sorts out these interconnections for you, so you don't
need to do much there yourself.
FPGAs have evolved from CPLDs (Complex Programma-
ble Logic Device). As a consequence of their internal
architecture, FPGAs have greater design flexibility com-
pared to CPLDs. On the downside, the increased flexibil-
ity has also increased the complexity.
However, don't be taken aback by the overwhelming
number of possibilities and accompanying data, descrip-
tions, tutorials and other things. Once you've started
with FPGAs, chances are that you cannot live without
them any more.
( 050324 - 1 )
The right microcontroller for every user
Florian Schaffer
The first steps into the world of micro-
processors seem to be easy at first
glance. Countless starter kits tempt the
prospective buyer with all sorts of bells
and whistles, but on closer examination
they tend to be much alike. A PCB with
a microprocessor, eight or more I/Os,
an RS232 port for communicating with
a PC and an LCD for the displaying of
text is pretty much standard. So when
choosing the hardware you cannot
really go wrong that much. But which
one do you choose?
Apart from the differences in price, not
too many things play a part when
choosing a development kit for person-
al use. If you are just starting out in the
world of microprocessors and are
about to buy your first kit, it is a good
idea to first think about what you
would like to achieve with the develop-
ment kit and how much scope there is
for expansion. Are you only going to
design a specific control system for
which the number of inputs and outputs
are already defined? Are you just hav-
ing a tentative look around and want
to try things out in a microprocessor
environment, do a little bit of program-
ming for some flashing LEDs and react
to pushbutton inputs, and get an LCD
to spring into life? Or do you need
some special functionality, such as a
serial port, a USB-interface or an Im-
port for data exchange with other
devices?
Depending on the purpose that you
have in mind for the board, you will
have to examine the various modules a
little closer. It is best if you do not just
rely on the brief technical datasheets
from the manufacturer, but also look at
the discussions in various Internet
forums to read user experiences. In that
way you get to find out the a particular
board does have an RS-232 interface,
but which is not very useful in real life
because the 8-byte buffer is too small
and the processor is much too slow to
receive and process more than four
symbols at data rates from 9600 baud
and up.
With this we arrive at the next criteri-
on: instruction set and speed of the
processor. For a heating control appli-
cation there is no need for the CPU to
calculate at great speed. If it gets
warmer a few seconds later, then that
is not a big deal. It is different if a few
thousand LEDs have to be driven via
some multiplex scheme. If the CPU is
not fast enough, the LEDs will just
appear to flash in some meaningless
fashion. If your program has to react
quickly to signals Trom the outside', for
example keyboard input or data from
an interface, then it can be handy if
the microprocessor is good at process-
ing interrupts.
Also think about the various program-
ming solutions. Do you need additional
hardware to program the microcon-
troller, can it be (re-) prog rammed in the
system (ISP - In System Programming)?
What method do you prefer?
What are your ambitions regarding tin-
kering with these things? Most develop-
ment kits consist of one PCB. The LCD
is connected with a ribbon cable and
the power supply consists of by a stan-
dard mains adapter, which is regulated
on the board with a 780x. With very
simple models it may even be possible
that you have to provide your own reg-
ulated power supply.
Perhaps you're looking for something
to do some control tasks in your home.
A module that has been designed for
rail/rack mounting, typically used in
electrical installations, can be very
practical. In order to realise your
plans, it is probably necessary that you
need more parts, which you will have
to build yourself or that are possibly
available read-made. Examples are a
stepping motor driver or a relay board
to control large loads.
After you have made your selection
with respect to the hardware, do not
forget to look at the software aspect.
Of course, for most of the microproces-
sors some form of development environ-
ment is available. The question is, how
much do you have to pay for it, and
with which programming language do
you have to work? Assembler is not
something everyone is familiar with. C
and BASIC are easier for beginners to
use and are certainly not worse,
although hardcore assembler hackers
will sometimes have a good laugh
about BASIC. The resulting machine
code ultimately loaded into the proces-
sor is not substantially different com-
pared to handwritten code. Because in
the beginning you will probably need
to rely on some help from other users,
it is best to have a look for a suitable
forum and see what sort of topics are
being discussed. The best way is to use
Google to search for forums that deal
with a specific type of controller.
It is possible that a development kit
contains a programming language that
in practice is not actually used in com-
bination with that kit, for example a C
development environment. If you have
questions in relation to that, it will take
much longer to get an answer if other
users use predominantly BASIC or
assembler.
In the forums there are always people
participating who are glad to help you
out. Most of the beginner's questions
have already been asked so it certainly
pays to do a search of the forums first.
In general you have to be prepared to
do a little searching to obtain a satis-
factory end result. You will also have to
trawl through numerous datasheets.
32
elektor electronics - 3/2006
Your price conscious PCB supplier
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Line Tracking Mouse £24.99
Uses an 8bit OTP CPU and
photo transistors to follow a line.
Sound Reversing Car £13.75
Using a mono-stable oscillator &
mic this car will react to sounds.
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BSr A small AM radio with ZX141
IC. With headphones.
Basic Solar kit £6.99
This kit includes a small solar panel.
“solar” motor, stickers & booklet.
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Make an astable oscillator which
flashes two sets of five LED’s
Photo Sensor & Relay £6.99
Make a kit that can turn an item
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Metal Detector kit
How does a metal detector work?
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We Also stock a range of lead free logic chips...
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Using a 555 and a 4017 chip
make an electronic dice.
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Using this kit you can listen to * f#
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FM Microphone £12.99
Build a short range FM
transmitter with microphone.
Crystal Radio £7.99
This is a great postcard
AM crystal radio. No soldering
Single Valve Radio £26.99
Build your own thermonic
valve AM radio. No soldering.
Infrared player £14.99
A two part kit which plays
music based on what button
is pressed on the remote.
Light Alarm £4.99
Using transistors, when this kit
sees light it makes a noise.
Music Firefly £8.99^^
soldering.
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This great surface mounted rework station
includes a 35W 200-480C temperature
controlled soldering iron, 100-500C
Hot air rework gun, 4 nozzles and a 0-15V
1 .5 A PSU. A must have unit!
Aoyue 936 Soldering Iron £24.99
A high quality temperature controlled
35W soldering iron with long lasting
ceramic heater element, metal iron stand
with solder holder/feeder. Spare element
included free! Temp range: 200-480C
Other tools and such Babani Books & More
Coil Design and Construction Manual £3.99
IC 555 Projects £4.99
25 Simple Indoor and Window Aerials £1 .75
25 Simple Tropical and MW Band Aerials £1.75
Getting the Most From Your Multimeter £3.99
An Introduction to Amateur Radio £4.99
How to Use Oscilloscopes £6.99
Projects for Radio Amateurs and SWLs £3.95
The Art of Soldering £3.99
A Beginners Guide to TTL Digital Ics £4.95
A Beginners Guide to CMOS Digital Ics £4.95
Practical Opto-Electronic Projects £4.95
Electronic Projects for Video Enthusiasts £4.95
Nuts & Volts US Electronics Magazine £4.99
Aoyue 850 hot air gun
£54.99
Smoke Extractor
£34.99
Workstation & PSU
£27.99
Aoyue suction pen
£3.50
2M Pb Free Solder
£1.99
4M Pb Free Solder
£2.99
35M Pb Free Solder
£7.99
Advanced Kits
AM Radio Kit & Case £13.99
AM/FM Radio & Case £16.99
DIY Multimeter Kit. £16.99
Multi-Output PSU kit £17.99
100ft TV Transmitter £27.99
Post and Packing
HEF4001BP: Quad 2-Input NOR-Gate DIL-14 29p
HEF4011BP: Quad 2-Input NAND-Gates DIL. 29p
HEF4013BP: Dual D-Type Flip-Flop DIL-14. 29p
HEF4015BP: Dual 4-Bit Register DIL- 16. 43p
HEF4017BP: 5-stage Johnson Counter DIL-16. 38p
HEF4021BP: 8-Bit Stat Shift Register DIL-16. 43p
HEF4028BP: 1 -of- 10 Decoder DIL-16. 40p
HEF4060BP: 14-Stage Binary Counter DIL 45p
HEF4069UBP: Hex Inverter DIL-14 29p
SN74HC00N: Quad 2-Input NAND Gate DIL 25p
SN74HC02N: Quad 2-Input NOR-Gate S DIL 25p
74HC03N: Quad 2-Input NAND Gates DIL-14 29p
74HC04N: Hex Inverter Buffered-Gate DIL-14 26p
74HC08N: Quad 2-Input AND-Gates DIL-14 26p
74HC10N: Triple 3-Input NAND Gates DIL 29p
SN74HC11N: Triple 3-Input Flip-Flop DIL-14. 25p
SN74HC14N: Hex Inverter CMOS DIL-14. 23p
74HC21N: Dual 4 Input AND Gate DIL-14. 29p
SN74HC74N: Dual D-Type Flip-Flop DIL-14. 25p
SN74HC245N: Octal 3-State Bus Transceiver . 42p
SN74LS00N: Quad 2-input NAND-Gate. 50p
SN74LS14N: Hex Inverter Bipolar DIL-14 50p
SN74LS32N: Quad 2-Input OR-Gate DIL-14 46p
SN74LS123N: Dual Mono-stable multi-vibrator 65p
SN74LS138N: 3-to-8 Line Decoder DIL-16 65p
SN74LS245N: Octal 3-State Bus Transceiver 76p
SN74LS373N: Octal D-Type Latch DIL-20 76p
Order Value
£4.99-£12.99
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P&P Cost
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Or visit our shop in Lichfield
3/2006 - elektor electronics
33
INFOTAINMENT
THE 6502
The Triumphant March
30-year old design still inspires thousant
Roelf Sluman
Are eight-bit processors something from the past or is it still possible to do some-
thing useful with them? Elektor Electronics went looking and discovered that the
good-old 6502, in a world of threaded computing and dual-core processors, still
has a following of faithful fans.
Figure 1.
The KIM-1 computer,
developed by MOS
Technology. Input was
via a hexadecimal
keyboard, for the
output a 6-digit LED
display was present.
In the 1970's and 80's three 8-bit processors dominated
the market: the 6809 from Motorola, the Z80 from Zilog
and the 6502 from MOS. By far the most popular of
these three was the
6502: its low cost (when r —
introduced, the 6502 set
you back about 25 dol-
lars) and the advanced
design for its time made
sure that the 6502 con-
quered the world in a
short time as the brain in
popular home-computers
such as the
Commodore 64 and the
Apple II.
elegant 8-bit processor. Many thousands of enthusiasts
across the whole world still work daily with the 6502
and make it do things that were not considered possible
1975.
in
Price war
When the 6502 was introduced In 1975 it cost
about 25 dollars. That made it a serious com-
petitor to the processor it was copied from, the
6800, which by comparison costs a whopping
1 79 dollars. No wonder computer manufacturers
such as Apple and Commodore went for the
6502. Steve Wozniak from Apple had his eye in
the 6800, but the enormous price difference ulti-
mately forced the decision.
We are now some 30
years later and proces-
sors that are many thousands of times faster than the
6502 now dominate the market. But... that does not
mean that there are no applications to be found for the
tylODULf
rr
hUt \Vjlk ^
r-
,T .
History
The 6502 processor cele-
brates its 30^ anniver-
sary this year. The intro-
duction was preceded by
a scandal: the designers
of the 6502 had, in the
first instance, developed
another processor: the
6501. Unfortunately, it
was a virtual copy of the
— _ — — _ — _ j 6800 processor from
Motorola. This is not a
surprise, because the same designers developed the
Motorola 6800! Shortly after the 6800 processor
appeared on the market, a dispute arose between
Motorola and the 6800 designers. This conflict resulted
in the resignation of most of the designers, who were
promptly hired by MOS Technology (in the 70's
Motorola's biggest competitor). MOS recognised the
potential for the 6800 and asked the designers to design
a processor that was pin-compatible with the 6800. That
became the 6501 , which was much cheaper because the
development costs were negligible.
Naturally, Motorola weren't going to just let that happen
and threatened to drag MOS into court. MOS responded
with the 6502, which was exactly identical to the 6501
with the only change that the pin-out was different. As a
consequence, the 6502 no longer fitted in boards that
were designed for the 6800, which was reason enough
for Motorola not to proceed with a lawsuit.
Because there were now no boards that would fit a
6502, MOS had to design something to bring the 6502
34
elektor electronics - 3/2006
the
Is of designers
to the attention of software developers. This
became the KIM-1 (see Figure 1), a single-board
computer with 1 kB of RAM.
Computer manufacturers quickly appreciated the enor-
mous potential that the 6502 offered. With the introduc-
tion of the Apple II and Atari 400 personal computers,
the 6502 broke into the American market; Commodore
was equally successful in Europe with the VIC-20 and
later the Commodore 64 (with a more advanced version
of the 6502, the 6510). The sales of just the Commodore
64 alone exceeds 25 million; the total number of 6502
processors sold worldwide is estimated at well over one
hundred million!
In Elektor Electronics there were also countless projects
using the 6502. The 'Junior Computer' was an exception-
ally successful learning system published in the 1980s.
From 1 983 there was a series of boards that allowed
you to build a complete 6502 computer. This finally
resulted in 1 985 in a system that was called Octopus 65.
The technology
puter with 64 kB of
memory that could be
switched in or out as
desired in an intelligent
manner, via a method called bank switching.. (For
example, in the memory area into which the I/O ports
were mapped there was also a section of RAM that could
be switched into 'view' so that data could be copied to it
and then switched 'out of view' so that the l/O-ports
were accessible again.)
Get cracking yourself with a 6502
The best way to get to know the 6502 is to work with
one yourself.
Simulator
The easiest way is using a simulator, a piece of software
that imitates the behaviour of a 6502. An example of an
excellent 6502 simulator is the program 6502 Simulator
that you can download free from
http://home.pacbell.net/michal_k/6502.html (Figure 2),
among others.
The 6502 is a 5-volts, 8-bit processor with a 1 6-bit
address bus, that with a range from 0x0000 to OxFFFF is
able to address up to 64 kB of memory. It comprises
4,300 transistors. The clock speed is 1 MHz, but
because the 6502 does not have to work through a list of
microcode instructions for each opcode that has to be
executed, it is in practice just as fast as a 4 MHz Z80
(which does use microcode).
Emulator
An emulator is a computer program that creates a so-
called virtual machine: a computer inside a computer as
it were. Because an emulator is a software replica of an
authentic computer or processor, all software written for a
certain computer or processor will also run in the emula-
tor. Even possible design faults that were present in the
The instruction set consists of no more than 56 instruc-
tions and because RAM memory was much faster in
those days, the designers saved on internal registers. The
6502 has therefore only three, each eight bits wide: the
accumulator (the only register on which operations can
be performed), and the index registers X and Y. The rela-
tively large number of addressing modes of the 6502
makes it possible to address 64 kB of memory efficiently,
using two-byte instructions (opcode and one operand). In
order to fill 64 kB of memory, not more than 1 9 bytes of
opcodes and operands are required. (Do you know
how? Send the author an email: rsluman@gmail.com!)
There exist a number of variations of the 6502, with
either more or fewer features. The best known are the
6507 (which was used in the Atari VCS2600 game com-
puter) and the 65 1 0 that can be found in the Com-
modore 64. The Commodore 64 was the first home com-
Figure 2.
Ideal for those who
want to work with a
6502: the 6502
macro-assembler and
simulator from
Michal Kowalski.
3/2006 - elektor electronics
35
INFOTAINMENT
THE 6502
Figure 3.
The old, trusty screen
from the Commodore
64, now as emulator on
a modern computer.
original hardware are present in the emulator!
Practically every computer from the 70's and 80's has
been emulated by now. In a large number of cases, the
software producers from the then popular computer soft-
ware have made their software freely available for use on
these emulators. If you're ever thinking nostalgically about
your time in front of your Apple, Atari or Commodore com-
puter then you can relive those times with an emulator!
One of the better-known emulator programs is VICE (a
rather silly abbreviation for Versatile Commodore Emula-
tor). This can be found at www.viceteam.org. VICE was
written to emulate all known Commodore home computers
(including the Commodore 64). The VICE emulator is so
perfect that practically every piece of software ever writ-
ten for the Commodore 64 runs flawlessly under VICE.
After starting VICE, the famous blue screen of the Com-
modore 64 appears (Figure 3). From now on you're
dealing with a real Commodore 64. Even the keyboard
Figure 4.
One of the two PCBs
that comprise the 6502
built from discrete
parts by Dieter Muller,
(source: website
Dieter's Hobby
Projects)
e
&
mb
l5" v 1 w ^ •
,Y ■- ■
- V - h in -
Figure 5.
At FPGA Arcade
various 6502 hardware
for games are emulated
in an FPGA.
has been arranged differently and now corresponds to
the Commodore 64 keyboard. The disk drive and cas-
sette player, including any possible turboloaders are also
completely emulated.
Copying
You can also copy a 6502 using 'discrete' components
such as 7400-series ICs, RAMs and EPROMs. This is
what Dieter Muller did with some old bits he had at
home. He nearly succeeded, using about 40 ICs and two
PCBs (Figure 4). The most important concession is a dif-
ferent timing, but his processor knows all 6502- and
65C02 opcodes (see http://people.freenet.de/
dieter.02/ m02.htm).
A different approach is to start with an FPGA and to
build into it the complete functionality of a 6502. An
36
elektor electronics - 3/2006
FPGA, after all, contains a large number of programma-
ble logic blocks and in a modern version the circuit for
an 6502 can be easily accommodated (or even multiple
copies in one FPGA!). There is an organisation, which
goes by the name Opencores, that is engaged in the
development of various CPU cores in FPGAs
(http://opencores.nnytech.net). The 6502 code can be
found after a bit of searching, it is called T65. This is also
available from http://www.fpgaarcade.com/, where
a number of games variations of the 6502 are available
as well (Figure 5).
Applications
Because the 6502 is such a versatile and cheap proces-
sor, and because it is easy to combine with other hard-
ware, it is still a favourite element in many DIY projects.
Many projects can be found on the Internet that use a
6502. Most of these comprise a home-built computer
with the 6502 as its nerve centre, but a number of very
inspiring applications can also be found...
The 6502 in the casino
That a 6502 can be used to make a lot of money was
discovered by the / Eudaemons / , a pair of American stu-
dents from California. They built two circuits based in the
6502, which they housed in two shoes. They subse-
quently went to a casino and picked a roulette table. Stu-
dent number one moved his shoe in the same rhythm as
the revolutions of the roulette wheel. The 6502 processor
in this shoe used a revolutionary algorithm to calculate
on which number the ball would come to rest. This infor-
mation was then automatically sent to student number
2 kB memory?
More than enough!
The first computer in which the 6502 was used
was the world famous games computer from
Atari, the VCS2600. Although the 6502 was
already the cheapest computer in its class. Atari
managed to reduce the price even further by
ordering a special version of the 6502, the 6507.
This processor could address a maximum of 8 kB
instead of the normal 64 kB. Not a problem,
according to the designers of the Atari 2600.
After all, memory was so expensive that no com-
puter game would ever use more than 2 kB.
two, who could determine, based on the vibrations in his
shoe, on which number to bet.
Give your robot eyes
Mike Naberezny used a combination of four Sharp
GP2D02 infrared sensors and a 6502 to give his robots
'eyes'. The program does nothing more than continually
poll the four sensors (high values mean 'close' and low
values mean 'far') and pass this information to the robot.
On the Internet (with as starting point www.6502.org)
many more such fantastic projects around the 6502 can
be found.
(050316-1)
Where can you find
a 6502 now?
Gunther Ewald
It is hard to believe, but microcontrollers with a
6502 core are still being produced today.
Manufacturers such as Micronas and Renesas use
this CPU core in cheap microcontrollers for simple
control tasks.
Have a look at Micronas at the WDC65C816 CPUs,
which are used mostly in automotive applications:
http://www.micronas.eom/products/by_function/c
dc_l 607f-e/product information/index. html
Renesas employs the 6502 core in the entire 740
family. These are (with exception of specific exten-
sions) completely opcode-compatible with the origi-
nal.
Unfortunately the selection has been reduced
somewhat as a result of switching to lead-free pro-
duction, but the manufacturer still has 37 deriva-
tives with a 6502-core:
www.renesas.com/fmwk.jsp7cnts740_family land-
ing.jsp&f p=/ products/ mpumcu/740_family/
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These products are not really suitable for hobby
applications. You need to use a special emulation
MCU and an emulator. The manufacturer does
make a free MCS-simulator available with a run-
time of 4 months. This offers l/O-simulation, inter-
rupt-simulation, execution cycle measurement, RAM
monitor display and coverage measurement. The
program is available from the Renesas homepage.
3/2006 - elektor electronics
37
HANDS-ON
MICROCONTROLLERS
Gunther Ewald
and Burkhard Kainka
In the February issue, we
described how you can get
started with the R8C/13
microcontroller module without all too
much effort. The application board
described here gives the module a 'base camp'
with lots of connections to the outside world,
including a USB interface and two serial ports. There's also an LCD interface and other
useful features for developing your own applications.
38
elektor electronics - 3/2006
The starting point for this design was
the question, what do you need to suc-
cessfully utilise all the major features of
the microcontroller with a minimum of
effort? The result is a circuit board with
the following complement of functions:
• two serial interface ports
• a USB port using an integrated
USB/serial adapter
• an LCD interface
• four LEDs that can be connected to
port lines
• a potentiometer connected to one of
the many analogue inputs
• a power supply socket and 5-V volt-
age regulator
• an option for powering the board via
the USB port
• a reset switch
• a jumper for the MODE input
The USB interface on the board deserves
special mention. Serial interfaces are
becoming increasingly rare on new PCs,
but asynchronous serial interfaces are
fundamentally necessary for communi-
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Figure 1. The circuitry on the application board provides two serial ports, a USB interface and an LC display to connect the R8C daughter board to the outside world.
3/2006 - elektor electronics
39
HANDS-ON
MICROCONTROLLERS
USB Port
050179-3- 12
Figure 2. Block diagram of the
Prolific interface converter.
cation with the microcontroller. For that
reason, we decided to simply include a
USB/serial adapter on the board.
In contrast to the equally viable
approach of using an external USB
adapter, this has the advantage of
allowing the board to be powered via
the USB port. A total of four jumpers
determine which serial interfaces of
the microcontroller are routed via the
RS232 ports or the USB port. For
instance, you can load and debug pro-
grams via the USB interface, or you can
use the USB interface for serial commu-
nication with the microcontroller and
your programs.
Microcontroller ports
The schematic diagram (Figure 1)
essentially shows the principal fea-
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Figure 3. The virtual COM interface in the
Windows XP Device Manager window.
tures of an R8C system as already
mentioned in the February issue. The
MODE jumper and Reset switch are
important features. Interface drivers
are also necessary for the RXD1 and
TXD1 leads of the debug interface,
which are routed here via JP7 and JP8
to allow either RS232 or USB to be
used. Depending on the jumper set-
tings, you can use either the MAX232
and connector K4 or the PL2303 USB
controller and a USB link.
In addition to the serial debug inter-
face (UART1), the R8C/13 has a sec-
ond, fully independent serial interface
(UARTO) that communicates via the
TXDO and RXDO leads. As is well
known, the MAX232 can handle more
than just two lines - in fact, it can han-
dle four. That’s why jumpers JP9 and
JP10 and a second serial interface con-
nector (K3) are on the board. You can
also select either RS232 or USB for the
UARTO interface.
Now for a few words about the micro-
controller ports. The microcontroller
leads are routed to single-row socket
headers in order to leave all options
open. However, specific functions have
also been assigned to most of the port
leads. Here 8-bit port P0 is intended to
be used for connecting the LCD mod-
ule, but it can of course be used for
some other purposes if you don’t need
an LCD. A standard alphanumeric LCD
can be driven in 4-bit mode using only
six port pins. Leads P0_2 to P0_7 are
thus used by the LCD.
P0_0 is reserved for the debug inter-
face (TXD1) and is only available for
user applications if the debug function
is not used. That still leaves P0_1. As
this lead can also be used as an ana-
logue input, a potentiometer providing
a variable input voltage of 0-5 V can
be connected to it via JP 13. A supple-
mentary protective resistor (R17) pre-
vents overloading if P0_1 is acciden-
tally configured as an output while
connected to the potentiometer. The
two jumper pins can also be used as a
measurement input. If you want to
connect a sensor that outputs both
positive and negative voltages, you
can use the potentiometer to adjust
the zero point to where you need it.
The four lower bits of Port 1 can be
connected to the four LEDs via
jumpers and series resistors. That’s
ideal for your initial programming exer-
cises, such as those described in the
February issue. If you haven’t already
tried the ‘blinker’ example program,
now’s your chance to get up to speed.
If you remove jumpers JP3-JP6, these
leads can also be used as four addi-
tional analogue inputs. Just add a few
lines of code, and you have a four-
channel digital multimeter with LCD
display!
A total of seven individual port leads
have been left open, but you’re bound
to think of a use for them. Applica-
tions such as an I_C or SPI interface
and the like can always use an extra
lead or two.
It takes a bit of juice
There are two options for powering the
board, which are selected using JP11.
Either you can use the power supply
connector (Kl) and voltage regulator
IC21, or you can use USB with its built-
in 5 V supply voltage.
If you’re using USB anyhow, it makes
sense to dispense with an external
power supply. However, a bit of cau-
tion is advisable here. According to the
USB specification, every USB down
port is supposed to be protected
against overloads by a PolySwitch pro-
tective device. However, painful expe-
rience proves that it just ain’t so. A
simple short on the USB supply line
results in a small puff of smoke from
the PC motherboard and causes the
corresponding down port to be perma-
nently disconnected from the supply
voltage. For cost reasons, manufactur-
ers obviously do nothing more than
placing small series resistors in the
supply tracks, which then simply melt
through.
For this reason, a PolySwitch protective
device (FI) rated at 100 mA is included
on the application board for the spe-
cific purpose of protecting the PC. That
creates peace of mind and allows you
to experiment in a relaxed mood.
USB interface
Next we come to the USB interface.
The PL2303X, which sports the desig-
nation ‘USB to Serial RS232 Bridge
Controller’, comes from the Taiwanese
manufacturer Prolific (sales rep: Glyn).
Attentive readers may recall having
already seen this Prolific IC in a built-
in, encapsulated form in an interface
converter cable described in the Sep-
tember 2005 issue of Elektor Electron-
ics.
This IC is a full-speed USB device for
USB 1.1 and thus compatible with the
more recent USB 2.0 interface. That
means the data transmission rate on
the bus is 12 Mbit/s. R5 connects the
40
elektor electronics - 3/2006
D+ lead of the USB connector to 3.3 V
to signal a full-speed device to the PC.
That causes the PC to load a driver for
a virtual serial interface. Such a driver
allows serial interfaces to be operated
at transmission rates up to 1,228,800
baud (that’s 1.2 Mbaud!). In line with
the capabilities of the R8C/13, various
standard baud rates are used here. The
virtual serial interface behaves exactly
the same as a real RS232 interface for
downloading and debugging programs.
Figure 2 shows the internal structure
of the IC, which consists of a USB
transceiver, a serial interface, and two
data buffers. The data buffers support
fast, uninterrupted data transfers, with
data blocks being packed into individ-
ual USB frames. It is also possible to
connect an I_C EEPROM to store user
configuration settings, but that option
isn’t used here.
The non-inverted RXD and TXD signals
are available at the serial side of the
converter and can be connected directly
to the R8C. The inputs of the PL2302X
are compatible with 3.3-V and 5-V logic
levels. The TXD, DTR and RTS outputs
provide either 3.3-V or 5-V logic levels,
depending on the voltage connected to
pin 4. In this case, this voltage is 3.3 V
from the internal voltage regulator of
the PL2303. That means the level
applied to the serial input of the R8C/13
is 3.3 V, although the level actually
expected there is 5 V. That’s permissi-
ble, though, because the R8C/13 can
also be operated at 3.3 V, and besides
that a 3.3-V signal at the RXD input of
the microcontroller is adequate even
when it’s operated at 5 V. All inputs of
the R8C regard any voltage above
0.2 V cc as a logic ‘high’ level.
Driver installation
You may have already used a Prolific
USB adapter with your system. In that
case, the interface will be recognised
as soon as the board is connected to
the PC. If it isn’t, or if you experience
problems using the USB port, you
should install the latest version of the
driver. You can obtain the driver by
downloading the file 050179-3-ll.zip
from the Elektor Electronics website
( www.elektor-electronics.co.uk ). It con-
tains the file ‘PL-2303 Driver
Installer.exe’.
Run the driver installer file before con-
necting the board. Any older version of
the driver present in the PC will be
deleted automatically when the new
driver is installed. The next time the
board is connected (or another inter-
Figure 4. Configuring the buffer sizes and COM port number.
face converter using the Prolific IC is
connected), Windows will automati-
cally locate the appropriate driver and
load it. After that, your PC will have an
additional serial interface that can be
used just like a normal RS232 interface.
If you have already installed several
such interface converters, Windows
will assign a high COM number to the
new virtual interface. In that case, it’s
recommended to use Advanced Set-
tings to rename the interface, for exam-
ple to ‘COM2’. You can usually ignore
any message saying that this interface
is already in use, because it refers to
another virtual interface that is not
used at the same time. All you need to
know is which serial interfaces are
actually present in your PC in hard-
ware form. For example, the PC used
for our tests had only COM1 present on
the motherboard, but it also had an
interface card with COM3 and COM4.
In that case it’s a good idea to name
the virtual interface ‘COM2’ (see Fig-
ure 3), especially since many older pro-
grams only support COM1 and COM2.
Problems with high COM numbers
have also been observed with the FDT
download program, so you should at
least keep the number in the single-
digit range.
In some cases it may be necessary to
configure the FIFO buffer of the virtual
interface to the smallest possible size
(Figure 4) in order to obtain reliable
communication. That’s because with a
large buffer size, it’s theoretically pos-
! COMPONENTS
| LIST
Resistors:
R1-R4,R7= lkD
R5 = 1 kfl5
1 R6 = 47kD
■ R8,R9,R10 = 4kD7
I R1 1 = 33kD
I R12 / R13 / R14 = 220kD
| R1 5,R1 6 = 27D
I R17= lOkfl
I PI ,P2 = lOkD
Capacitors:
C 1 -04,08,0 1 1 ,C 1 2,C 18 = lOOnF
05,06 = lOpF
07,09,013 = 1 OjLtF 16V radial
■ CIO = 220|iF 25V
I C 1 4-C 1 7 = 4|iF7 25V radial
I Semiconductors:
| D1-D4,D6 = LED
l D5 = 1 N4002
D7 = 1N4148
IC1 = PL2303X (Prolific)
IC2 = 7805
IC3 = MAX232
Miscellaneous:
JP3-JP6JP1 2 = jumper
JP7-JP1 1 = 3-way SIL pinheader
K1 = 2-way PCB terminal block, lead
pitch 5mm
K2 = USB socket, type B for PCB
mounting
K3,K4 = 9-way sub-D socket, angled
pins, PCB mount
K5-K8 = 16-way SIL pinheader
K9 = LCD module, 2x16 characters
SI = pushbutton with 1 make contact
(e.g. TS695)
FI = 100 mA Polyfuse
X2 = 1 2MHz quartz crystal
PCB, bare, order code 050179-1
PCB, ready-assembled and tested, order
code 050179-92
LCD with backlight, order code
030451-72
Poly-LED display, order code
030451-73
3/2006 - elektor electronics
41
HANDS-ON
MICROCONTROLLERS
Figure 5a. The track and ...
42
elektor electronics - 3/2006
o o o o o o o o
^/o (b c o
P1.0
OO I Analog
050179-1
COM port
programming
Power LED
Contrast LCD
TxDI
PO.1
P0.2
P0.3
mod
P0.4
P0.5
P0.6
P0.7
IVcc
P3.0
AVss
P3.1
AVcc
P3.2
P3.3
7
7
Figure 5b. ... component layouts of the double-sided circuit board.
Figure 6. The fully assembled prototype board. The component overlay is slightly different from the production version shown in Figure 5.
3/2006 - elektor electronics
43
HANDS-ON
MICROCONTROLLERS
sible for the PC software to be
waiting for reply while the
query is still stuck in the buffer.
If errors occur when download-
ing programs into the flash
memory of the microcontroller,
reducing the size of the buffer may
improve the situation.
Board assembly
The printed circuit board (Figure 5) is
also available fully assembled so
readers with relatively little soldering
experience don’t have to worry about
problems with the Prolific IC (IC1),
which is only available in a 28-lead
SMD package (SSOP-28). If you assem-
ble the circuit board yourself, you
should start with this IC because it’s
easier to solder if the board is other-
wise empty.
Numerous Elektor Electronics SMD
projects have shown that they can be
soldered without using special SMD
tools. Start by soldering two diagonally
opposite leads in place, after first care-
fully positioning the IC. A check with
a loupe will show whether you have a
steady hand. If necessary, you can still
adjust the position relatively easily at
this stage. Continue by soldering an
entire row of leads with a sufficient
amount of solder. Any excess solder
can be easily removed afterwards with
a length of solder wick. If your final
inspection with a loupe does not reveal
any solder bridges, everything is OK.
The author has also found that strong
reading glasses (3 dioptre) are an
excellent alternative to a loupe.
They’re almost as good as stereo
microscope, at only a fraction of the
price.
The remaining components shouldn’t
present any special difficulties. You
can omit the pin headers (K5 and K8) if
desired. If you wish, you can later con-
nect flat cable here or wire only the
connections you actually need to the
prototyping area. A socket header has
proven to work well as an LCD connec-
tor. The matching LCD module can
then be fitted with long pin headers
and simply plugged into the board.
Initial test
Before using the board for the first
time, you should re-inspect the compo-
nent assembly and solder joints and fit
the necessary jumpers. The following
jumper settings are important:
JP 11:
toward K7/K8
(‘ext’ position,
with power coming
from an external supply)
JP 3-6: fitted (LEDs
connected)
JP 12: fitted (‘Power’ LED
connected)
JP 2: fitted (debug mode)
JP 7-10: toward IC3 (both interfaces
via RS232)
You should check the supply voltage on
the board before plugging in the
R8C/13 daughterboard, in order to
avoid any risk to the microcontroller.
LED D6 should light up after you con-
nect an AC adapter with 9-V DC out-
put. The voltage measured on I<6
between pin 5 V ss (Pin 5) and pin 7
(V cc ) must have a value of +5 V. After
verifying this, disconnect the AC
adapter and plug in the daughter board
while no power is applied to the board.
Now comes the most exciting moment!
Reconnect the 9-V AC adapter. The
‘Power’ LED will light up. Connect I<4
to the COM1 serial port of the PC. You
can immediately download a program
now, because JP2 is configured for
debug mode. Use the FDT program as
described in the February 2006 issue of
Elektor Electronics. A good choice for
your first download is the ‘port_toggle’
program. The programming tool will
indicate whether the download
process completed successfully.
Next, remove jumper JP2 and briefly
press the Reset button. The four LEDs
connected to Port PI should start
blinking.
If you want to use the USB interface, fit
JP7 and JP8 in the proper positions
(toward the USB connector). That will
connect RXD1 and TXD1 to the USB
converter IC. After that, you must con-
figure FDT to use the virtual COM
interface. Everything else works
exactly the same as with a real RS232
interface.
KD30 debugger
Up to now, we’ve only described how
to download finished programs into
the microcontroller and run them.
When you’re developing a program,
especially one that’s relatively com-
plex, it’s helpful to use a debugger.
That allows you to interrupt the pro-
gram at any desired location, view
memory contents, execute single
steps, and much more.
The microcontroller must always be in
debug mode when you use the debug-
ger, which means that jumper JP2
must remain fitted. The Reset button
isn’t necessary in this case, because
you can only use software commands
from the debugger to start and stop
your program.
We’ve prepared an extensive descrip-
tion of how to get started with the
debugger and placed it on the Elektor
Electronics website at www.elektor-
electronics.co.uk. Deeopnding on the
amount of feedback we get, a special
R8C activity page may also be created,
so check out the website.
( 050179 - 3 )
References:
www.glyn.com
www.glyn.de
E-mail: elektor-r8c@glyn.de
R8C forum:
For hints and tips about using the
R8C/1 3 board, check out the 'R8C 1 6-
bit Micro Starter Kit' topic in our Forum
menu at www.elektor-electronics.co.uk.
Naturally, we would be pleased if you
post your own tips and tricks on this
forum for the benefit of other readers.
44
elektor electronics - 3/2006
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3/2006 - elektor electronics
45
HANDS-ON
MODDING & TWEAKING
Cheap Logger
Use a web router to read the
gas/water/electricity meters
Jeroen Domburg & Thijs Beckers
This month we'll turn an inexpensive router into a data logger. This is provided with sensors
that monitor the readings on gas, water and electricity meters. One of the benefits of using a
router is that the logger can be connected directly to an internal computer network and can
therefore be accessed from any PC with an Internet browser.
every five minutes, making it possible
to create nice graphs from the data. In
this way you can find out during which
part of the day the consumption is
highest, which can lead to better use
of the resources and smaller utility
bills.
The device itself can be permanently
fixed close to the meters. All measure-
ments can be accessed via the built-in
web server, programmed specifically
for this task. The meter reader can
therefore be hooked up to the home
network and accessed from any com-
puter.
The router used is again the ‘Sweex
broadband router’ with four 100 MBit
ports, type number LB000021 (without
WLAN). The reason we’ve chosen this
router is that it is still one of the cheap-
est available (£ 17.50 from scan.com).
The rest of the hardware isn’t pricey
either: the costliest are the microcon-
troller (an ATTiny2313 made by Atmel,
The Sweex LB000021 is still one of the cheapest routers that can run
Linux. At the time of writing, this model was available on the Internet for
less than £20, including postage costs.
When we look inside this router we see a pair of unpopulated headers on
the board. The smaller of the two (circled in red) is the serial port, which
well use for this project.
This is the board with the microcontroller, which well hook up to the port.
The circuit is so simple that it can easily be built on a piece of
experimenter's board.
In last month’s article
we described an inex-
pensive router and
showed how it could
be reprogrammed with
our own firmware.
This month we’ll use
the same router, with
some additional elec-
tronics, and build a
gas, water and elec-
tricity consumption
meter.
This meter
has four sen-
sor inputs
and can
therefore
read a maxi-
mum of four
meters. The
consumption
is read out
and stored
46
elektor electronics - 3/2006
The board is connected to the serial port and fixed to the router PCB using a folded piece
of duct tape. There is no need to use expensive screws or other fasteners.
A multitool is ideal for making the hole in the case for the sensor cables. A cable-tie
around the cables functions as a strain relief.
The router is connected, ready for the firmware update. The network cable connects
directly to a PC. This UTP cable may be either a crossover cable or a 1:1 cable.
tu_
R1
U b 0
TxD 0 -
RxD 0 -
GND 0
D1
D2
D3
11
100|i
20
©
RESET
PB7
PB6
PDO |C1
PB5
PD1
PB4
PD2
PB3
PD3
PB2
PD4
PB1
PD5
PBO
PD6
ATTiny2313
o
X
XI
D4
which should be available for a few
pounds) and the sensors.
This project consists of three parts: the
router itself, which acts as web server
and stores the data, the board with the
microcontroller, and the sensors. The
router communicates with the micro-
controller every five minutes. The lat-
ter uses sensors to keep track of the
meters.
The sensors are optical and the types
used depend on the meter they have to
read. The general idea is that the sen-
sor ‘looks’ at the gas, water or electric-
ity meter.
Most modern electricity meters have
an LED, which flashes every time a
certain amount of power has been con-
sumed. This pulse can of course be
easily detected by a simple LDR. Older
meters have a rotating disc with black
XI = 20MHz
Figure 1 . The microcontroller circuit is fairly simple and can easily be built on a piece of
experimenter's board (see inset).
Once everything is connected, the router can be found
at IP address 192.168.2.1. The firmware can be
upgraded to the GWE-meter firmware by selecting
'firmware upgrade' from the 'tools' menu.
It works! With the firmware upgraded, the router
can be connected to the network. The ex-router will
be given an IP address automatically. Take a look at
the configuration of your gateway, router or
cable/ADSL modem to find out what the address is.
3/2006 - elektor electronics
47
HANDS-ON
MODDING & TWEAKING
The time has come to connect the sensors. A modern
electricity meter with a flashing LED is the easiest...
An LDR covered by a piece of duct tape is sufficient to
obtain an accurate reading.
markers. These meters can be read
with the help of reflective optical sen-
sors such as the CNY70, or the OPB704
(more expensive, but better).
Gas and water meters usually have a
mark on one of the least significant
digits (often the ‘0’ or ‘6’). A reflective
sensor can be used without too many
problems in these cases as well.
Whichever type of method is used for
the measurements, all sensors occa-
sionally exhibit a drop in their resist-
ance. The capacitors connected to the
sensors (see Figure 1) and some clever
firmware in the microcontroller enable
these resistance changes to be read.
The firmware keeps track of the num-
ber of times that the current drops
below a certain value and hence how
often a change of resistance has
occurred. This count gives a good indi-
cation of the consumption over a given
time. The counters can be read or reset
via the serial port of the microcon-
troller. The calibration of the sensors
also takes place via this route.
The microcontroller’s serial port is con-
nected to a header in the router (JP2).
This header normally isn’t mounted on
the board. The serial port of the router
ends up at this header (see Figure 2).
The router itself runs a dedicated ver-
sion of the firmware. The firmware
contains a program that takes care of
the communications with the micro-
controller and makes sure that the
counters are read at the right time. As
we mentioned earlier, this occurs every
five minutes. The data are stored in the
internal RAM of the router. This has
the advantage that about a year’s
worth of data can be stored; the disad-
vantage is that all this data will be lost
if there is a power cut. Luckily, this can
easily be prevented by the inclusion of
a back-up battery in the power supply;
this will be covered in detail later on.
The firmware inside the router con-
tains a simple web server and several
server-side scripts; these enable every-
thing, including the network settings
and sensor calibrations, to be accessed
via a browser. It is also possible to use
the browser to view the data in differ-
ent formats. The data of one or more
selected sensors can be viewed as a
graph. Alternatively, the raw data can
be downloaded as a CSV file, for use in
Excel.
The facility to update the firmware
hasn’t been forgotten either. Using this
update facility, the official Sweex
firmware can be flashed back into the
router, so it can be used again as a nor-
mal router. It’s worth noting that the
meter firmware hasn’t stopped the
internal switch from working: the four
LAN ports and the WAN port are con-
figured as a single switch by this
firmware.
So far so good, but how can you obtain
this firmware? The answer is very sim-
ple: the required firmware is available
from both the Elektor website [1] (file
number 050360-11. zip), and the
author’s own site [2]. The Linux kernel
and all other tools used are licensed
under the GPL (General Public
License), which means that the source
code of the programs has to be made
available along with the firmware. The
author has of course complied with
this requirement. He has also made the
tools available that were written
specifically for use with the meter
firmware. These can also be down-
loaded from the above-mentioned
sites.
Installing the firmware is fairly simple:
the router already has a facility to
upload a firmware upgrade and this
method can also be used to smuggle
our firmware into the router; refer to
the inset for more info. If you want to
flash the original firmware back into
the router, you can use the method
The circle of the '6' in this gas meter is not filled
in, which can be detected by a reflective optical
sensor.
The reflective sensor is fixed to the meter using a
bit of Blu Tack.
48
elektor electronics - 3/2006
This water meter is a lot more difficult to read: there are no
distinguishable digits, no flashing LEDs...
In principle it should be possible to use a reflective sensor to
detect a dial, possibly using a blue LED. However, this has
not been extensively tested by the author.
described earlier.
The microcontroller can be pro-
grammed via the parallel port of a PC
and a programmer [3], consisting of a
DB25 connector and three resistors.
The required programming software is
available for Windows as well as other
operating systems.
The physical placement of the sensors
depends very much on the type of
meter they’re used with. A meter with
a flashing LED is easiest: an LDR can
be stuck with tape over the LED. A gas
or water meter can be trickier, but as
long as the reflective sensor can point
JP2
4m
1: RxD
2: +3V3
7: TxD
8: GND
Figure 2. These ore the connections
of JP2 in the router.
+U, N D1 +Ub
© | ©
050360 - 2 - 17
Figure 3. The back-up supply is inserted into the
supply line. This diagram shows that it is a fairly
simple circuit.
straight onto the last digit, it shouldn’t
cause too many problems either. The
author couldn’t test an electricity
meter without an LED (i.e. , one with
just a rotating disc), but it is likely that
the black marker on the disc can be
detected by a reflective sensor after a
bit of experimentation.
Once the sensors have been fixed into
place and connected to the microcon-
troller, they have to be calibrated.
There is a link on the web page of the
router that helps with this. This func-
tion continuously reads the (analogue)
value of the sensor until the user has
determined that the calibration is com-
plete. The minimum and maximum sig-
nal levels are extracted from these
readings. Each time that a sensor’s
output changes by more than two-
thirds of the difference between mini-
mum and maximum, the microcon-
troller assumes that another unit of
gas, water or electricity has been used.
There is no need to worry that the
router itself will significantly increase
your electricity bill: it only draws about
340 mA from its 12 V supply. The
power consumption is therefore about
5 watts. The router itself contains a
switch-mode PSU; any voltage from 6
to 15 Volts was found to be suitable.
Armed with this information, we can
design a simple back-up circuit to keep
the data safe during a power cut. A 9 V
NiMH or NiCd battery can keep the
router powered for some 20 minutes.
Six beefy NiMH cells give a back-up
time of about three hours. During this
period the meter continues to take
readings. The measurements of all con-
nected meters are therefore preserved.
The circuit in Figure 3 shows how a
back-up supply should be connected.
This circuit should be inserted
between the adapter and the router.
The two diodes ensure that no current
can flow from the adapter to the bat-
tery and vice versa. The resistor pro-
vides enough current to the battery to
keep it fully charged during normal
Web links
[1] www.elektor-electronics.co.uk/,
items March 2006.
[2] http://sprite.student.utwente.nl/
~jeroen/ projects/ gwemeter
[3] http://sprite.student.utwente.nl/
~jeroen/ projects/ progavr
use. If you use Schottky diodes the
voltage drop, and hence the losses, are
kept to a minimum. The value for the
resistor is calculated as follows:
R =
(LT b - C7 batt ) / (0.02 x battery capacity)
For example, when a 12-V adapter and
9-V battery with a capacity of 800 mAh
are used, the resistor should take a
value of about 180 Q.
( 050360 - 2 )
About the
author:
Jeroen Domburg is currently
studying electronic engineering
at the Saxion University in
Enschede (The Netherlands). He
is an enthusiastic hobbyist,
who spends much of his spare
time on microcontrollers,
electronics and computers. In
this section we will be able to
examine and build some of his
projects.
3/2006 - elektor electronics
49
Karel Wa I raven
Recharging batteries for devices such as digital cameras can be a problem when you're on
holiday in a remote or inhospitable region. You won't find an electrical outlet anywhere.
Naturally, you can count on an Elektor Electronics designer to whip up a solution using a solar
panel and a DIY Li-ion battery charger.
I was due a bit of a holiday, so I sug-
gested to management that I’d step
out for half a year. Their response was
less than enthusiastic, and my own
enthusiasm was soon dampened when
I had a good look at what it would
cost. The outcome was thus four
weeks of trekking through the Anna-
purna region in Nepal.
To meet my electrical energy needs, I
took along a solar panel and a simple
Li-ion charger built from discrete com-
ponents. I didn’t have a lot of time, and
in the spirit of the motto ‘better a good
copy than a bad design’, I cribbed the
accompanying circuit from a well-
known Chinese company.
As you doubtless know, charging
lithium cells is actually quite easy. You
generate a well-regulated voltage of
exactly 4.1 or 4.2 V (always read the
manufacturer’s specifications to deter-
mine the right value) and add current
limiting to keep the current within
bounds. The charging current will
automatically decrease as the cell
becomes charged (see Figure 1 for the
charging characteristic).
You can assume that the cell is fully
charged when the charging current
drops to 1/20C or less. Just to reiterate,
the charging voltage is critical - the
allowed tolerance is only 1%. That’s
not very much, because 1% of 4.2 V is
only 42 mV. That means you have to
measure the output voltage carefully to
ensure that it stays within tolerance.
The nice thing about this circuit (Fig-
ure 2) is that it’s easy to build as a DIY
project because it doesn’t use any
obscure components. The TL431 volt-
age reference is an old standby that
you can obtain almost everywhere. For
the rest, it consists of a few ordinary
transistors and a power transistor, all
of which can be replaced by any rea-
sonable equivalents. The Schottky
diode can be any type that can handle
1 A, or if necessary you can use an
ordinary 1N4001. The input voltage
can also be higher, although beyond a
certain point you’ll have to fit a heat
sink for Tl.
Design philosophy
It’s always interesting to examine
someone else’s design carefully in
order to figure out the underlying
design philosophy.
50
elektor electronics - 3/2006
Reference voltage
To start with, the circuit is based on a
good, stable reference voltage gener-
ated by a Texas Instruments TL431
(IC2). That’s a prudent choice,
because a good reference is a funda-
mental requirement if you want to be
sure of achieving 1% accuracy for the
charging voltage.
The reference IC is followed by an
emitter follower (T4) so the reference
source can supply more than just a few
milliamperes. That would normally
reduce the output voltage by approxi-
mately 0.6 V and trash the stability, but
feedback from the transistor via R21
and R23 eliminates those problems.
The IC adjusts its reference potential
to maintain a voltage of 2.5 V on its
Adjust input. That yields a reference
voltage of 3.3 V, which is used every-
where in the circuit. It’s important to
be able to adjust the value of R21 or
R23 when you’re building charger if
the voltage of the TL431 differs too
much from the nominal value. If a
check reveals that your reference IC is
near the end of the tolerance range,
correct the reference voltage by fitting
a resistor in parallel with R21 or R23.
You can simply use the trial-and-error
method by trying a succession of val-
ues until you obtain the correct volt-
age. Once that’s done, you can solder
the resistor permanently in place.
Naturally, a reference voltage of 3.3 V
represents an arbitrary choice. It could
also be a bit higher or a bit lower. It
shouldn’t be all too high, though, to
avoid restricting the headroom of the
TL431. A more important consideration
is that the reference voltage must fall
within the common-mode input volt-
age range of the opamp used in the cir-
cuit. We’ll say more about that when
we talk about selecting the opamp.
A decidedly low reference voltage,
such as 2.5 V (as obtained without a
voltage divider), is also undesirable
because it makes it more difficult to
drive LED D1 and increases the sensi-
tivity of the circuit to the input offset
voltage of the opamp.
Control circuitry
Now we come to the actual control cir-
cuitry. We want to have:
• a stable output voltage
• current limiting
• battery monitoring (for temperature)
• a clear indication when the battery
is fully charged
Figure 1. Charging characteristic of an Li-ion cell (source: Panasonic).
Figure 2. The circuit of the charger uses standard components instead of special charger ICs.
3/2006 - elektor electronics
51
TECHNOLOGY
LABTALK
Figure 3. The small printed circuit board for the charging circuit.
The spring contacts for the battery pack are at the right.
The first three items all affect the out-
put voltage. The output current can be
reduced by lowering the output volt-
age, and if the battery becomes hot,
the charging current must be reduced
by lowering the output voltage.
Here we have a topology in which
three opamps (IClb, IClc and ICld)
can simultaneously control a single
output. That’s possible using a sort of
OR-gate arrangement. In the
schematic diagram, you can see that
the outputs are simply connected
together. Under normal conditions,
that would naturally lead to problems
whenever one opamp tries to increase
the output voltage while another one
tries to reduce it. That problem can be
solved by putting diodes or transistors
after the opamps.
In this case, a more elegant solution is
to use opamps with open-collector out-
puts. That means each opamp can only
reduce the voltage on the shared out-
put. Resistor R8 provides the pull-up
voltage. It supplies the base current for
T2, which in turn drives T1 into conduc-
tion and voila, the positive terminal of
the battery is connected to the positive
supply voltage. This gives us a system in
which each parameter (voltage, current,
and temperature) has its own opamp
that can reduce the output voltage.
Current regulation
As a rule of thumb, you can assume
that the maximum charging current of
a normal Li-ion battery is around 0.7 to
1 times its capacity. This charger deliv-
ers a maximum current of 0.65 A,
which makes it suitable for batteries
rated at 0.65 Ah or more.
The current with a fully discharged
battery would ordinarily be higher
than the above-mentioned 0.65 A. The
current can be easily measured by con-
necting a small resistance in series.
Here that role is fulfilled by R17 and
R18, with two resistors being used due
to the magnitude of the current and
the power dissipation. The current
generates a voltage across these resis-
tors, and ICld compares this voltage
with a reduced reference voltage
obtained from a voltage divider. If the
voltage generated by the charging cur-
rent is higher than the comparison
voltage, ICld takes control by reducing
the voltage on the shared output. That
lowers the charging voltage for the
battery and thus reduces the charging
current to the desired level.
When the battery becomes fully
charged, the control function provided
by IClc prevents the voltage from ris-
ing above 4.2 V. The battery voltage is
compared with the reference voltage
via two voltage dividers (R15/R16 and
R7/R4, respectively), and if necessary
IClc reduces the voltage on the
shared output.
The logic of the temperature monitoring
circuitry with IClb is similar. A thermis-
tor (NTC resistor) is built into the bat-
tery, and its resistance decreases as the
temperature increases. The thermistor
forms a voltage divider in combination
with Rl, and IClb compares the voltage
at the junction of this divider with a
reduced reference voltage obtained
from divider R14/R3. It restricts the
charging process if the temperature
rises too high.
By the way, this temperature protec-
tion is not fail-safe, so charging will
proceed as normal if there is bad con-
tact or an open lead.
If you’ve ever built a circuit with an
opamp followed by two transistors
(which also provide gain), you know
you can expect problems. Such a cir-
cuit is guaranteed to oscillate. That
problem is solved here by using a hefty
capacitance (Cl) to slow down the
entire control loop. An additional
capacitor (C2) connected at the output,
in combination with voltage divider
R15/R16, keeps the circuit stable in the
no-load state, and the divider provides
a minimum load.
Indicator
We haven’t said anything yet about the
indicator portion of the circuit, which
consists of the circuitry around ICla.
This bit of electronics is not essential
to the operation of the circuit, but it is
nevertheless very important. As a user,
you naturally want to know where
things stand. The nice thing about this
indicator is that it responds to the
charging current. That means you can
be sure that charging is actually taking
place, which avoids simple errors such
as forgetting to connect the mains
adapter or a bad battery contact.
Here again the reference voltage is
divided down, this time by R12/R19, to
a voltage of approximately 14 mV If the
voltage drop resulting from the charg-
ing current through R17/R18 is less
than this value (with no battery con-
nected or a fully charged battery), the
internal open-collector output transis-
tor of ICla will be cut off. The red LED
in D1 will be off in that case, but the
green one will be on because it is con-
nected to 3.3 V and to ground via a
220-fl resistor.
In the opposite case, with sufficient
charging current flowing, ICla will pull
its output low. In that case LED will be
on and T3 will conduct to short out the
green LED and keep it dark. Using a
bi-colour LED for D1 thus provides a
perfectly clear charging indicator.
Have you already realised the signifi-
cance of selecting 14 mV as the refer-
52
elektor electronics - 3/2006
ence voltage for ICla? The maximum
charging current of 650 mA generates a
voltage drop of 153 mV across
R17/R18. 14 mV is approximately 1/11
of this value, so the battery is consid-
ered to be fully charged as soon as the
current drops to 1/11 of the maximum
value. The charging process will con-
tinue as usual, but the LED will indi-
cate that the battery is fully charged.
You could also add another stage to
the circuit, because it’s better to limit
the charging current to 1/10 of the
battery capacity if the battery has
been discharged to below 2.9 V. That
can be easily implemented by using
another opamp to connect a resistor
in parallel with R5 to reduce the
divided reference voltage for current
limiting to 14 mV. However, the man-
ufacturer decided not to do this, pre-
sumably because it would require an
additional IC.
Component selection
Now for a few remarks about select-
ing the opamp. When you design a
circuit, you can choose from hundreds
of IC types. All the different options
don’t make the choice any easier.
However, in this case a standard
opamp type without any special prop-
erties is sufficient. It doesn’t need to
have especially high accuracy (a mil-
livolt more or less doesn’t matter), it
doesn’t have to have a special tem-
perature range, and noise and speed
are also unimportant. However, there
are two aspects that deserve further
attention.
The first is the common-mode range.
When you select an opamp for a cir-
cuit, it’s important to keep all the volt-
ages that may be present on its inputs
within the limits of the common-mode
range, or to select an opamp that can
handle the expected range of voltages.
The data sheet for the LM399 says that
the lower limit is 0 V and the upper
limit is 1.5 V below the supply voltage.
If we had chosen an LM741, the lower
limit would have been 1.5 V, so a volt-
age such as 14 mV would not have
been allowed. That means it’s essen-
tial to chose an opamp for this design
that can work properly with voltages
close to zero.
The second aspect is the offset volt-
age. From the data sheet, you can see
that the input offset voltage is 2 mV.
(The manufacturer supplies this
opamp in various versions with differ-
ent offset voltage ratings. As you
might expect, better specs always
cost more.) That means the IC intro-
duces an error of approximately 2 mV
at its inputs. As a result, although you
think (or hope) that the charging indi-
cator will change state at 14 mV, it
may actually change as early as 16 mV
or not until 12 mV. That’s an error of
more than 10%, which is considerable.
That isn’t a problem for the charging
indicator, but such an error in the
charging voltage would be unaccept-
able. That’s why the reference value
for the charging voltage is much
higher at around 2.4 V. An error of
2 mV at 2325 mV is only around 1 part
in a thousand, which is negligible.
( 050396 - 1 )
CONSTRUCTIO
Elektor Electronics (Publishing) does not provide parts and components
other than pcbs, fornt panel foils and software on diskette or ic (not neces-
sarily for all projects). Components are usually available form a number of
retailers - see the adverts in the magazine.
Large and small values of components are indicated by means of one of
the following prefixes :
E (exa) = 10 18
P (peta) = 10 15
T (tera) = 10 12
G (giga) = 10 9
M (mega) = 10 6
k (kilo) = 10 3
h (hecto) = 10 2
da (deca) = 10 1
a (atto) = 10~ 18
f (femto) = 10“ 15
p (pico) = 10“ 12
n (nano) = 10“ 9
H (micro) = 10“ 6
m (milli) = 10“ 3
c (centi) = 10“ 2
d (deci) = 10 _1
In some circuit diagrams, to avoid confusion, but contrary to iec and bs
recommandations, the value of components is given by substituting the rel-
evant prefix for the decimal point. For example,
3k9 = 3.9 ka 4/x7 = 4.7 /xF
Unless otherwise indicated, the tolerance of resistors is ±5% and their rat-
ing is l A- l A watt. The working voltage of capacitors is > 50 V.
In populating a pcb, always start with the smallest passive components,
that is, wire bridges, resistors and small capacitors; and then ic sockets,
relays, electrolytic and other large capacitors, and connectors. Vulnerable
semiconductors and ics should be done last.
Soldering. Use a 15-30 W soldering iron with a fine tip and tin with a resin
| core (60/40) Insert the terminals of components in the board, bend them
■ slightly, cut them short, and solder: wait 1-2 seconds for the tin to flow
1 smoothly and remove the iron. Do not overheat, particularly when solder-
ing ics and semiconductors. Unsoldering is best done with a suction iron
or special unsoldering braid.
1 Faultfinding. If the circuit does not work, carefully compare the populated
] board with the published component layout and parts list. Are all the com-
N GUIDELINES
ponents in the correct position? Has correct polarity been observed? Have
the powerlines been reversed? Are ah solder joints sound? Have any wire
bridges been forgotten?
If voltage levels have been given on the circuit diagram, do those meas-
ured on the board match them - note that deviations up to ± 10% from the
specified values are acceptable.
Possible corrections to published projects are published from time to time
in this magazine. Also, the readers letters column often contains useful
comments/additions to the published projects.
The value of a resistor is indicated by a colour code as follows.
color
1st digit
2nd digit
mult, factor
tolerance
black
0
brown
1
1
xlO 1
±1%
red
2
2
xlO 2
±2%
orange
3
3
xlO 3
-
yellow
4
4
xlO 4
-
green
5
5
xlO 5
±0,5%
blue
6
6
xl06
-
violet
7
7
-
-
grey
8
8
-
-
white
9
9
-
-
gold
-
-
xlO- 1
±5%
silver
-
-
XlO- 2
±10%
none
—
—
—
±20%
Examples:
brown-red-brown-gold = 120 D, 5%
yellow-violet-orange-gold = 47 kD, 5%
3/2006 - elektor electronics
53
HANDS-ON
Erik Martens
What turns a mC board into a real PLC? A PLC is a controller with a program stored in memory,
where reliability, availability and safety are of the utmost importance. Only when a mC board
can be operated as a PLC and it complies with industrial standards can it be called a real PLC.
This project covers all aspects to turn
a standard AT89S8252 jliC board into a
real PLC, using a minimum of off-the-
shelf components. To add the PLC
functionality to an AT89S8252 board
we require a small section of extra soft-
ware (firmware) in the microcontroller.
Your own jliC PLC program then works
under supervision of this firmware.
System overview
To turn a standard AT89S8252 board
into a PLC we make use of four I/O
pins on the microcontroller (P1.0 to
PI. 3). When the controller is reset it
knows from the state of the flip-flop
(IC2a and IC2b, read via P1.0) whether
a hardware reset or an internal reset
occurred. After a hardware reset the
firmware sets the flip-flop using Pl.l.
Port Pl.l also turns off all output sec-
tions (a high level from Pl.l turns off
T1 via IC3d and IC2d).
The STOP/RUN/RESET switch (SI) is
used by the firmware to start and stop
the PLC program. This switch can also
be used (via R3) to force a hardware
reset of the jliC. P1.2 is used to read the
state of the STOP/RUN/RESET switch.
When the switch is in the STOP posi-
tion, all outputs are automatically
turned off. LEDs D7 and D8 show the
current status of the PLC program.
Should the level of the supply voltage
to voltage regulator IC4 drop below
about 8.2 V, it will be reported to the
jliC via P1.3, after which all output
modules are immediately turned off.
Two input modules have been
included in the circuit diagram, but
you can add as many as you need to
ports PO, P2 or P3. The inputs are elec-
trically isolated, can take +24V DC sig-
nals, are protected against voltage
spikes and polarity reversal.
The output sections are also electri-
cally isolated. You can connect as
many output modules as you need to
ports PO, P2 or P3. However, the output
sections can only be active when T1
conducts. This will only happen when
all operating conditions are satisfied
(Pl.l and PI. 2 high, STOP/RUN/RESET
switch in the RUN position and a high
enough supply voltage).
To program the jliC you can use the
SPI port (PI. 5, PI. 6 and PI. 7) on the
jliC. The programming can only take
place when the reset line is active.
For this reason R8-R11 and IC3a have
been added, so that a high RS232
input (for example DTR) will keep the
jliC reset line permanently high. The
programming functionality via the
SPI port is not shown in the circuit
diagram.
Firmware
The main PLC program works under
supervision of the so-called firmware.
An example of this firmware has been
included in this article and you will find
it to be relatively small (about 100
bytes). The jliC PLC firmware was writ-
ten using the TASM shareware assem-
bler. The use of this assembler has been
covered in previous Elektor articles:
‘89S8252 Flash Microcontroller Board’
(Dec. 2001), ‘Microcontroller Basics
Course’ parts 1 and 2 (Jan./Feb. 2002).
These articles also describe the differ-
ent ways in which the microcontroller
software can be put into the microcon-
trollers (external programmer, SPI).
The firmware takes care of the follow-
ing functions:
Reset
After a reset the jliC will immediately
start running the firmware. If a hard-
ware reset occurred, the PLC will start
the first PLC cycle if all other conditions
are satisfied (STOP/RUN/RESET switch
in the RUN position and a good supply
voltage). When an internal reset occurs
(when the cycle time was exceeded),
the STOP/RUN/RESET switch first
needs to be set to the STOP position,
and then to the RUN position, before
the PLC cycle will start again
Please note: this project is has not been tested or post-engineered by the Elektor Electronics laboratory.
54
elektor electronics - 3/2006
R3
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030158-11
Figure 1. Circuit diagram of a real PLC using an AT89S8252.
RUN-STOP function
The most important task of the
firmware is to make sure that all con-
ditions are satisfied before starting a
PLC cycle. A PLC cycle can be started
if the following conditions are met:
• the STOP/RUN/RESET switch is in
the RUN position;
• the supply voltage is high enough;
• the STOP/RUN/RESET has been
switched from RUN-STOP-RUN after
the PLC cycle time has been
exceeded.
STOP/RUN/RESET switch
This switch is used to control the run-
ning of the PLC program. When the
switch is turned to the STOP position
the currently running cycle is still com-
pleted, after which no new PLC cycle
is started. When the PLC is in the
STOP condition all output modules are
turned off.
Supply voltage monitoring
Before the start of every PLC cycle
the firmware checks that the supply
voltage is (still) in order. Should the
supply voltage at the input of voltage
regulator IC4 drop below about 8.2 V,
a new PLC cycle will not begin and
the ERRPS routine will be called
instead. This routine can be used to
store variables into a non-volatile
memory (the EEPROM in the jaC)
before the supply voltage drops too
far for the jliC to stop functioning. If
there is only a temporary drop in volt-
age (caused by interference, for
example), which doesn’t reset the jliC,
the PLC cycle will start again as soon
as the supply voltage is restored.
PLC cycle-time watchdog
You may know that the AT89S8252
has an on-chip watchdog timer. This
timer is used to keep an eye on the
cycle time of the PLC program. At the
start of every PLC cycle the watchdog
timer is reset. Should a PLC cycle take
too long, for example caused by an
endless loop within the PLC program,
the internal watchdog will generate
an internal reset of the jliC . In the
reset state of the jliC Pl.l will immedi-
ately become ‘high’, which causes all
output modules to be turned off. The
firmware will then detect that an
internal reset occurred (by the state of
flip-flop IC2a/b) and will enter the
STOP condition. Despite the fact that
the STOP/RUN/RESET switch is in the
RUN position, the PLC program will
remain in the STOP condition. The
program only exits from this condition
when the STOP/RUN/RESET switch is
turned to STOP. This behaviour pre-
vents the PLC from starting again
immediately after the PLC cycle time
3/2006 - elektor electronics
55
HANDS-ON
was exceeded. The maximum PLC
cycle time can be set to one of the fol-
lowing values: 16, 32, 64, 128, 256,
512, 1024 or 2048 ms.
Using the |iC PLC firmware
Listing 1
ORL WMCON, 0000 100 OB set EEMEN, select uC EEPROM
MOV DPL, #010H
MOV DPH,#000H
MOVX A,@DPTR store contents of address 16 into the accumulator
The PLC firmware included with this
article should be used as the basis for
r m as ™
your own PLC application. You only
1 Listing 2
■
need to add your code to the MAIN,
■
1
MOV
DPL,#010H
INIUC, INIPLC, ERRPS and ERRCY rou-
■
1
MOV
DPH , #000H
tines to provide the functionality you
1
ORL
WMCON, #00010000B
require.
1 M001
MOX
A, WMCON
I
JNB
ACC. 1,M001
MAIN: This routine is called every
I
MOV
A, B
cycle. This is where the inputs are
1
1
MOVX
@DPTR, A
read, the logical relationships are
■
1
ANL
WMCON, #11101111B
set EEMWE , write-enable uC EEPROM
wait until the uC EEPROM is ready
reset EEMWE , write-disable uC EEPROM
calculated and the outputs are set.
The MAIN routine may not run
longer than the set watchdog time,
so take care with delay loops and
‘jumping back’.
INIUC: When power is first applied to
the jliC PLC this routine is called once.
You could for example use this routine
to restore variables from the EEPROM
of the microcontroller. The example
below shows how to get the contents
of EEPROM address 16 and store it in
the accumulator (see Listing 1).
INIPLC: This routine is called once
when the STOP/RUN/RESET switch is
set to the RUN position (warm start).
You could use it to initialise certain
variables with a starting value. You
could also initialise a communication
link here. The cycle time is not moni-
tored while this routine is running.
Figure 2. Monitoring the supply voltage.
ERRPS: The ERRPS routine is called
once when the supply voltage is
turned off or when it falls below a
critical level. In this routine you could
store permanent variables (these are
variables that have to keep their
value during a power failure) into the
microcontroller EEPROM. The follow-
ing example shows how the value of
the B register is stored in the micro-
controller EEPROM at address 16
(see Listing 2).
ERRCY: This routine is called continu-
ously when the cycle time has been
exceeded and the STOP/RUN/RESET
switch is in the RUN position. This rou-
tine could be used to light an LED that
indicates that a program error has
occurred. This LED should be extin-
guished again in the INIPLC routine.
And finally...
This project forms the basis of a real
PLC, where you are free to add a large
number of input and output modules
according to your requirements. It also
complies with industrial standards for
signal interfacing, operation and control.
The source code for the controller
firmware has been made freely avail-
able to Elektor Electronics readers by
the author. This file can be down-
loaded from our website under no.
030158-11.
( 030158 )
N Attention! ]\\
This project uses a transformer that is connected to the mains supply. This could have deadly
consequences if you don't comply with all relevant safety standards. For this reason it's important that
you follow all instructions shown on the safety guidelines page, regularly printed near the back of the
magazine. When you use the transformer recommended in this article you can mount the circuit into a box
that complies with the Class-ll standard.
56
elektor electronics - 3/2006
Listing 3. An
example of the firmware in the 89S8252.
; FIRMWARE mC PLC
WMCON
.equ
096H
P1.0
.equ
090H
Pl.l
.equ
091H
PI. 2
.equ
092H
PI. 3
.equ
093H
■org
0000H
start address after a reset
LJMP
START
■org
0200H
; RESET mC
START
ANL
WMCON, #11111110B
disable watchdog
JB
PI. 0, SOFT
jump, software reset
; HARDWARE RESET mC
HARD
CLR
PI. 2
disable outputs using PI. 2, because Pl.l will be used to set the reset-flipflop
CLR
Pl.l
set the reset-flipflop
JNB
P 1.0, HARD
jump, wait until the reset-flipflop is set
SETB
PI. 2
enable outputs using PI. 2
ACALL
INIUC
mC initialisation following a reset
SJMP
NCYC
; SOFTWARE RESET mC
SOFT
ACALL
ERRCY
STOP/RUN/RESET switch in RUN position after the cycle-time was exceeded
JB
PI. 2, SOFT
jump, wait for the STOP/RUN/RESET switch to be in the STOP position
ACALL
INIUC
mC initialisation following a reset
SJMP
NCYC
jump, STOP/RUN/RESET switch was set to STOP
;PLC CYCLE
PLC
JNB
PI. 2, NCYC
jump, STOP/RUN/RESET switch is set to STOP
JB
PI. 3, NCYC
jump, faulty supply voltage
SJMP
WDTR
jump, conditions are met to start a new PLC cycle
NCYC
ANL
WMCON, #11111110B
disable watchdog
SETB
Pl.l
disable outputs using Pl.l
JNB
PI. 3, PSOK
jump, supply voltage OK
ACALL
ERRPS
faulty supply voltage
PSNOK
JB
P1.3, PSNOK
jump, wait until the supply voltage is OK
PSOK
MOV
R2,#100
delay: #100 x #50 x 2ms = 10.000ms = 10ms
DELO
MOV
Rl,#50
DELI
DJNZ
Rl.DELl
DJNZ
R2.DEL0
JNB
PI. 2, NCYC
jump, STOP/RUN/RESET switch is in STOP position
JB
PI. 3, NCYC
jump, faulty supply voltage
ACALL
INIPLC
PLC initialisation after the STOP/RUN/RESET switch is set to RUN,
or when the supply oltage returns
CLR
Pl.l
enable outputs using Pl.l, STOP/RUN/RESET switch is set to RUN
and the supply voltage is OK
ORL
WMCON, #11100000B
WMCON: ms WMCON: ms
#000xxxxx 16 #100xxxxx256
#001xxxxx 32 #101xxxxx512
#010xxxxx 64 #110xxxxxl024
#011xxxxx 128 #lllxxxxx2048
ORL
WMCON, #00000001B
enable watchdog
WDTR
ORL
WMCON, #00000010B
watchdog-timer reset
;PLC PROGRAM
MAIN
LJMP PLC ; jump, next PLC cycle
INITIALISE mC -called once after a hardware reset
INIUC RET
INITIALISE PLC (STOP/RUN/RESET switch set to RUN or return of the supply)
INIPLC RET
;POWER SUPPLY ERROR -called once after the supply fails
ERRPS RET
;CYCLE TIME ERROR (STOP/RUN/RESET switch set to RUN after the cycle-time is exceeded)
ERRCY RET
3/2006 - elektor electronics
57
TECHNOLOGY
E-BLOCKS
Figure 1.
Initial specification
sketch.
John Dobson
E-blocks SPI Bus Board containing NVM and DAC
Many of you may be familiar with using the A/D inputs of the PICmicro microcontroller but
using D/As is less common. This short article examines how it is possible to use Flowcode
and E-blocks to produce a simple sinewave oscillator for use in testing audio circuits.
There is often a requirement for a simple sinewave oscil-
lator you can use for testing audio circuits. The E-blocks
system includes a D/A converter (DAC) so why not make
a general-purpose waveform generator with it?
To start with, you need to decide on the range of values
you want to produce and do some calculations on the
overall parameters to check the project is feasible. The
D/A has an output range of 0 to 5 V in 255 equal steps.
It does not make sense to go too near the supply rails in
case some headroom is needed for a buffer device, so to
keep things simple, go for a maximum of 4 V peak-to-
peak output. This can be divided down in software to get
Samples 63 127 191 255
Angle 7C/2(90°) 71(180°) 371/2(270°) 271 (360°)
smaller signals. The frequency will need to be around
1 kHz - that's mid-range audio. A quick check of the
specification of the MAX5385 D/A states that it has a
settling time of 20 jis for an output accuracy of "half of
the least significant bit". If we have 256 samples per
waveform then this would give us a maximum output fre-
quency of 200 Hz. In theory that's not high enough, but
as we are using a sinewave, with small incremental steps
between samples, the system has a fighting chance of
coping and we can always resort to reducing the number
of samples per waveform if it does not perform well.
Get to grips with D/As
Good news: D/As are relatively simple to use. You feed
them a number and the analogue output level equals the
full-scale voltage output multiplied by a ratio, N, of the
number you feed in and the full-scale digital input. From
the graph in Figure 1 you can see an initial sketch
assuming 5-V full scale output and eight bits (2 8 = 256 or
0 to 255) input. Actually, the output of the DAC is only
0.9 V cc so there will be a 1 0% voltage level error in the
real output, but we can live with that.
The micro needs to generate a range of values corre-
sponding to a sinewave output. With 256 steps that
means 256 separate values. Fortunately, sinewaves are
symmetrical as well as periodical so we can actually just
58
elektor electronics - 3/2006
generate numbers for a quarter of a waveform and then
use simple programming to reflect the data horizontally
and vertically. We want a 4-V peak-to-peak output — to
make the numbers easy it's best to actually just use a
range of 200 of the available 256 bits. This will give us
close to 4 V out of the full (theoretical) 5-V range. The
core waveform is shown in the bottom left of Figure 1 : it's
64 values in 'x' with a digital range of 0 to 1 00, or
around 2 V.
At this stage we need to use a spreadsheet to calculate
the numerical output values for the core data.
The formula for a sinewave is y - sin(x), where x varies
from 0 to 360 degrees or 0 to 271 radians. Unable to fig-
ure out how to get Excel to work in degrees here at Elek-
tor labs we just used radians. We've only shown the first
three and last three of the 64 core values. To get the val-
ues you need to send to the DAC, just multiply sin(x) by
the core range of 1 00.
Okay, so that's the theory over.
In practice
First, let's look at the hardware. We're going to be using
the E-blocks SPI bus Board shown in the introductory
photograph. This goes onto the Multiprogrammer board
which happens to have a PIC16F877 on it. You could
use almost any PIC with a USART. The SPI board goes on
port C and we have an LC display on port B and a key-
pad on port D.
The SPI board has a MAX5385 DAC as well as a 64-
kByte SPI bus and non-volatile memory (NVM). You may
first want to get the data into the NVM. As a future exten-
sion of the project, consider building up a portfolio of dif-
ferent waveforms inside the NVM and then call them up
separately as needed using the keypad and LCD for
selection.
To populate the NVM, a program was written that stuffed
the core 64 data values into the NVM. A counter from
0-63 was set up, followed by a routine that writes indi-
vidual bytes of data to sequential NVM locations. In
Flowcode this is quite easy, you just initialise the SPI bus
and then write a program with 64 icons, each of which
writes a byte of data, as shown in Figure 2.
The next step will be to write a separate program to
check that the core values produce the first quarter of the
sine wave. This was fairly straightforward - again a
counter is established, reading the value from NVM loca-
tions 0 to 63 in turn, followed by a routine forwarding
the data from the NVM to the DAC. The Flowcode that
did it may be seen in action in Figure 3.
The oscillogram in Figure 4 shows you the first output
waveform for the first quarter cycle. It's a bit rough
around the edges but looks like a quarter of a
sinewave. Unfortunately the time period for a quarter
cycle was 3 ms - giving a final frequency of under
Figure 2. NVM stuffing program.
Figure 3. Simple program to take NVM data and send it to the DAC.
3/2006 - elektor electronics
59
TECHNOLOGY
E-BLOCKS
Figure 4. First output waveform showing repeated core values being output.
Table 1 - output values
Sample no.
X
sin(x)
1 00sin(x)
0
0.024544
0.024541
2
1
0.049087
0.049068
5
2
0.073631
0.073565
7
• • •
• • •
• • •
• • •
61
1.521711
0.998796
100
62
1.546255
0.999699
100
63
1.570798
1
100 ,
1 00 Hz; too slow for our purposes. Oh well - we have
a backup plan.
Towards the goal
Things are slowed down by the need to serially read the
data from the external NVM. However, the '877 device
we're using also has 256 internal bytes of EEPROM!
What we can easily do is fill the PIC's internal EEPROM
with our data, which hopefully will speed up the process
a great deal.
A new user macro called LOADEEPROM was added to
Flowcode. It reads the external NVM and puts the
64 data bytes into internal EEPROM. Consequently the
program was altered to read data forwards for the first
quarter, and backwards for the second quarter of the
waveform. Next, an offset of 127 is added and the data
for the second half of the cycle was manipulated simi-
larly. We then measured the results, which you can see in
Figure 5.
The final signal has a period of 2.5 ms or a frequency of
400 Hz, and a peak-to-peak voltage of around 3.5 V.
The waveform does not look too distorted although at the
zero-crossing points you can see a small discontinuity.
This is presumably caused by program delays between
each quarter cycle of data being read out. This may be
solved by loading the internal EEPROM with the full
256 databytes and start the waveform at 90 degrees
where distortion will have less effect. Let us and others
know how you tweaked the project to perfection — post
your findings with E-blocks in Elektor's online Forum.
( 065031 - 1 )
Earlier in this series
Electronic Building Blocks, November 2005.
E-blocks and Flowcode, December 2005.
E-blocks in Cyberspace, January 2006.
E-blocks — now you CAN, February 2006.
Articles may be downloaded individually from our website.
Figure 5.The final output.
Programs available
for download
SPI memory stuffing.fcf
First quarter.fcf
Sine wave gen.fcf
SPIscreen.FCF
File number: 065031-1 l.zip
Location: MAGAZINE — > March 2006 'E-blocks
Making Waves'.
60
elektor electronics - 3/2006
In all mains-operated equipment certain
important safety requirements must be
met. The relevant standard for most
sound equipment is Safety of Informa-
tion Technology Equipment, including
Electrical Business Equipment (Euro-
pean Harmonized British Standard BS
EN 60950:1992). Electrical safety under
this standard relates to protection from
• a hazardous voltage, that is, a volt-
age greater than 42.4 V peak or
60 V d.c.;
• a hazardous energy level, which is
defined as a stored energy level of
20 Joules or more or an available
continuous power level of 240 VA
or more at a potential of 2 V or
more;
• a single insulation fault which would
cause a conductive part to become
hazardous;
• the source of a hazardous voltage
or energy level from primary power;
• secondary power (derived from
internal circuitry which is supplied
and isolated from any power
source, including d.c.)
Protection against electric shock is
achieved by two classes of equipment.
Class I equipment uses basic insu-
lation ; its conductive parts, which may
become hazardous if this insulation
fails, must be connected to the supply
protective earth.
Class II equipment uses double or
reinforced insulation for use where
there is no provision for supply protec-
tive earth (rare in electronics - mainly
applicable to power tools).
The use of a a Class II insulated
transformer is preferred, but note that
when this is fitted in a Class I equip-
ment, this does not, by itself, confer
Class II status on the equipment.
Electrically conductive enclosures
that are used to isolate and protect a
hazardous supply voltage or energy
level from user access must be protec-
tively earthed regardless of whether the
mains transformer is Class I or Class II.
Always keep the distance between
mains-carrying parts and other parts as
large as possible, but never less than
required.
If at all possible, use an approved
mains entry with integrated fuse holder
and on/off switch. If this is not avail-
able, use a strain relief (Figure, note 2)
on the mains cable at the point of entry.
In this case, the mains fuse should be
placed after the double-pole on/off
switch unless it is a Touchproof® type
or similar. Close to each and every fuse
must be affixed a label stating the fuse
rating and type.
The separate on/off switch (Figure,
note 4), which is really a ‘disconnect
device’, should be an approved double-
pole type (to switch the phase and neu-
tral conductors of a single-phase mains
supply). In case of a three-phase sup-
ply, all phases and neutral (where used)
must be switched simultaneously. A
pluggable mains cable may be consid-
ered as a disconnect device. In an
ELECTRICAL SAFETY
INFO & MARKET
1. Use a mains cable with moulded-on plug.
2. Use a strain relief on the mains cable.
3. Affix a label at the outside of the enclosure near the mains entry stating the
eguipment type, the mains voltage or voltage range, the freguency or fre-
guency range, and the current drain or curent drain range.
4. Use an approved double-pole on/off switch, which is effectively the ‘discon-
nect device’.
5. Push wires through eyelets before soldering them in place.
6. Use insulating sleeves for extra protection.
7. The distance between transformer terminals and core and other parts must
be >6 mm.
8. Use the correct type, size and current-carrying capacity of cables and wires
- see shaded table below.
9. A printed-circuit board like all other parts should be well secured. All joints
and connections should be well made and soldered neatly so that they are
mechanically and electrically sound. Never solder mains-carrying wires
directly to the board: use solder tags. The use of crimp-on tags is also good
practice.
10. Even when a Class II transformer is used, it remains the on/off switch whose
function it is to isolate a hazardous voltage (i.e., mains input) from the pri-
mary circuit in the eguipment. The primary-to-secondary isolation of the
transformer does not and can not perform this function.
approved switch, the contact gap in the
off position is not smaller than 3 mm.
The on/off switch must be fitted by
as short a cable as possible to the
mains entry point. All components in
the primary transformer circuit, includ-
ing a separate mains fuse and separate
mains filtering components, must be
placed in the switched section of the
primary circuit. Placing them before the
on/off switch will leave them at a haz-
ardous voltage level when the equip-
ment is switched off.
If the equipment uses an open-con-
struction power supply which is not
separately protected by an earthed
metal screen or insulated enclosure or
otherwise guarded, all the conductive
parts of the enclosure must be protec-
tively earthed using green/yellow wire
(green with a narrow yellow stripe - do
not use yellow wire with a green stripe).
The earth wire must not be daisy-
chained from one part of the enclosure
to another. Each conductive part must
be protectively earthed by direct and
separate wiring to the primary earth
point which should be as close as pos-
sible to the mains connector or mains
cable entry. This ensures that removal
of the protective earth from a conduc-
tive part does not also remove the pro-
tective earth from other conductive
parts.
Pay particular attention to the metal
spindles of switches and potentiome-
ters: if touchable, these must be protec-
tively earthed. Note, however, that such
components fitted with metal spindles
and/or levers constructed to the rele-
vant British Standard fully meet all insu-
lation requirements.
The temperature of touchable parts
must not be so high as to cause injury
or to create a fire risk.
Most risks can be eliminated by the
use of correct fuses, a sufficiently firm
construction, correct choice and use of
insulating materials and adequate cool-
ing through heat sinks and by extractor
fans.
The equipment must be sturdy:
repeatedly dropping it on to a hard sur-
face from a height of 50 mm must not
cause damage. Greater impacts must
not loosen the mains transformer, elec-
trolytic capacitors and other important
components.
Do not use dubious or flammable
materials that emit poisonous gases.
Shorten screws that come too
close to other components.
Keep mains-carrying parts and
wires well away from ventilation holes,
so that an intruding screwdriver or
inward falling metal object cannot touch
such parts.
As soon as you open an equipment,
there are many potential dangers. Most
of these can be eliminated by discon-
necting the equipment from the mains
before the unit is opened. But, since
testing requires that it is plugged in
again, it is good practice (and safe) to
fit a residual current device (RCD)*,
rated at not more than 30 mA to the
mains system (sometimes it is possible
to fit this inside the mains outlet box or
multiple socket).
* Sometimes called residual current
breaker - RCB - or residual circuit cur-
rent breaker -RCCB.
These guidelines have been drawn up
with great care by the editorial staff of
this magazine. However, the publishers
do not assume, and hereby disclaim,
any liability for any loss or damage,
direct or consequential, caused by
errors or omissions in these guidelines,
whether such errors or omissions result
from negligence, accident or any other
cause.
3-core mains cable to BS6500 1990 with three stranded
conductors in thick PVC sheath
Max current
3 A
6 A
13 A
conductor size
16/0.2 mm
24/0.2 mm
40/0.2 mm
Norn cond area
0.5 mm 2
0.75 mm 2
1.25 mm 2
overall cable dia.
5.6 mm
6.9 mm
7.5 mm
Insulated hook-up wire to
DEF61-12
Max current
1.4 A
3 A
6 A
Max working voltage
1000 V rms
1000 V rms
1000 V rms
PVC sheath thickness
0.3 mm
0.3 mm
0.45 mm
conductor size
7/0.2 mm
16/0.2 mm
24/0.2 mm
Norn cond area
0.22 mm 2
0.5 mm 2
0.95 mm 2
overall wire dia
1.2 mm
1.6 mm
2.05 mm
3-flat-pin mains plug to BS 1363A
3/2006 - elektor electronics
61
HANDS-ON
EAVESDROPPING
Galvanic isolation is a
special feature of this
telephone amplifier, which
includes a line output
connection for a hi-fi system.
From an idea by
Markus Muller
Although in some countries, including
the UK and Germany, analogue tele-
phone connections are something of a
dying breed, most residential cus-
tomers use analogue apparatus, even
in cases where the underlying connec-
tion is over ISDN.
There is little reason to change: first,
ISDN telephones are rather expensive,
and second, ISDN connection starter
packs generally include an a/b adap-
tor which allows the connection of old
analogue telephones to the ISDN sys-
tem. What a lot of analogue tele-
phones lack, and which most modern
ISDN devices provide, is a loud-
speaker.
The experienced Elektor Electronics
reader will have no difficulty in
adding a loudspeaker. Several
designs for telephone amplifiers have
appeared previously in Elektor Elec-
tronics, but there has never been a
circuit to which we cannot make
some improvements or add new and
interesting features.
High Voltage
The amplifier described here has the
special feature, not shared by any of its
predecessors, of a line output. This
means that it can be connected to an
ordinary hi-fi system. This requires, as
a glance at the circuit diagram in Fig-
ure 1 will show, complete galvanic iso-
lation between the telephone network
and the mains. Now we shall look at
the parts of the circuit in turn.
The amplifier has two RJ45 telephone-
style sockets connected in parallel at
its input, to simplify adding the circuit
into an existing cabling arrangement.
An analogue telephone connection
works essentially as shown in Fig-
ure 2. In the quiescent state the
exchange provides a DC voltage of
nominally 60 V between the a-wire
and the b-wire. The actual voltage
level varies significantly with the dis-
tance from the exchange and can be as
low as 40 V or as high as 80 V. To ring
the telephone to signal an incoming
call, the exchange superimposes an
AC voltage of up to 75 V on the DC
level. The peak value of the ringing
voltage can thus be over 120 V. Despite
the low current available, this is dan-
gerous: not just to humans, but also, in
particular, to connected electronic
devices. When the receiver is lifted, a
current of between 10 mA and 30 mA
flows and the DC voltage falls to
around 12 V. The analogue voice signal
is superimposed on this voltage.
Private telephone exchange systems
and a/b adaptors can work at much
lower DC voltages (often 24 V)
because the distance to the telephone
itself is much shorter.
Amplification and filtering
Of course, the telephone amplifier
must be designed to work at any of
these voltages. It is the noble duty of
input capacitor C2 to isolate these DC
levels from opamp IC1 (an LF356). A
high-voltage type is essential, and the
component recommended in the parts
list can easily cope with 400 V.
Next we must ensure that the AC
component is also reduced to a level
62
elektor electronics - 3/2006
an advanced amplifier
with line output
safe for the input to IC1: this is achieved using
two Schottky diodes, D1 and D2, which limit the
incoming voltage to between -0.3 V and 15.3 V.
The current which flows is limited to a safe value
for the diodes (and for the exchange) by R3. The
reduced AC voltage (whether it be a ring signal
or a voice signal) is taken to the inverting input
of inverting amplifier IC1 via R4. Since the useful
signal can vary considerably in level, the gain of
the amplifier can be adjusted between 0 and 2
(which is slightly lower than might be expected,
on account of C2 and C4) using potentiometer PI.
At the same time, a DC voltage of 6.8 V is applied
to the non-inverting input of the amplifier by volt-
age divider R1/R2. This voltage can be measured
for test purposes at the output of the opamp. This
voltage, which is a little less than half the supply
voltage, is used at another point in the circuit
where it is not allowed to exceed 7 V. The output
swing of the opamp is such that this small asym-
metry does not matter.
Since the telephone voice signal is not exactly
high-quality audio, we can take some liberties
with it in the interests of reducing the effects of
interference and noise. The input capacitor, along
with R3 and R4, forms a high-pass filter with a cut-
off frequency of 100 Hz, while C3 and R3 form a
low-pass filter with a corner frequency of about
17 kHz. And last but not least, C4 also attenuates
higher frequencies above about 10 kHz (or at least
those which the opamp is capable of amplifying).
Galvanic isolation
To protect the output stages and any electronics
that may be connected to them, two type 6N138
linear optocouplers are used to provide galvanic
isolation up to 2.5 kV. Since the performance of the
optocouplers is not very dependable (in that their
characteristics vary considerably from one device to
the next), we use the rather elegant combination
of two 6N138s shown to achieve repeatable opera-
Figure 1. The telephone and audio parts of the circuit are kept strictly separate.
3/2006 - elektor electronics
63
HANDS-ON
EAVESDROPPING
Figure 2. AC and DC voltages on an analogue telephone line.
Measured characteristics
Characteristic curve A shows the frequency response of the telephone
amplifier. The measurement was made at the line output, and thus
corresponds to the values for the loudspeaker output. The upper fre-
quency range is shown for the two extreme settings of PI, and the
effect of capacitor C4 is clearly visible. The -3 dB frequency of
9.9 kHz (at -20 dB) falls to 6.8 kHz when PI is set to maximum.
At the low-frequency end the effect of the loudspeaker is significant.
With the loudspeaker connected the corner frequency is 1 40 Hz,
whereas without the loudspeaker it is 1 00 Hz. Since the output
impedance of the TDA7052 amplifier effectively attenuates the out-
put signal by about 1 dB, we have artificially superimposed the
curves so that they may be compared more easily.
Here are some of the characteristics as measured on the prototype:
d
B
r
+3
-0
-3
-6
-9
-12
-15
-18
-21
-24
-27
-30
-33
-36
-39
-42
Line output (LSI not connected)
With LSI (8 Q) connected
Sensitivity
Maximum output level
Maximum bandwidth
Minimum bandwidth
Minimum THD+N
THD+N
Signal-to-noise ratio
Signal-to-noise ratio
Full drive, 1 V line level 60 mV
THD+N = 1 % 1.6 V
100 Hz to 9.9 kHz
140 Hz to 6.8 kHz
B = 22 Hz to 22 kHz 0.26 %
B = 22 Hz to 22 kHz, LSI = 8 a 1 %
250 mV in, 1 V out, B = 22 Hz to 22 kHz 55 dB
250 mV in, 1 V out 57 dBA
P max (THD+N = 1 %) Voice signal 750 mW
Minimum THD+N B = 22 Hz to 22 kHz 0.6 %
Signal-to-noise ratio at 500 mW, B = 22 Hz to 22 kHz 55 dB
Signal-to-noise ratio at 500 mW 57 dB
Quiescent current consumption 72 mA
Current consumption at P max 0.3 A
Current consumption when overdriven maximum 0.4 A
Minimum supply voltage 9 V
64
elektor electronics - 3/2006
tion. The optocouplers have a Darling-
ton pair at the output and are con-
nected so that the current flowing
through the output of IC2 is coupled
back via IC3 to the input of IC2.
Although this arrangement is slightly
noisy, the circuit has adequate band-
width and the gains in terms of linear-
ity and low distortion more than com-
pensate.
The current though IC2 is translated
into a voltage for the following output
amplifier by R8. C9 removes the DC
component of the signal on R8, and
also forms a second high-pass filter
with a relatively low corner frequency
of approximately 40 Hz. This makes the
overall frequency response of the
amplifier fairly flat. C8 also reduces
interference from the power supply, a
point which we shall return to later.
As we stated earlier, the gain of the
input stage of the circuit is approxi-
mately 2. The attenuation in the opto-
coupler is approximately 4.7, and so
the overall gain up to the volume con-
trol potentiometer P2 is around 0.4.
This attenuation is not a problem since
the gain of IC4 (in bridge mode) is
39 dB. The optimum voltage at the out-
put of the optocouplers, in terms of
minimising THD+N, is around 100 mV.
At this voltage distortion (the second
harmonic is below -53 dB) is compara-
ble with the signal-to-noise ratio of
-55 dB. At maximum volume (P2 at
maximum), IC4 is overdriven.
Output amplifier
The familiar Philips TDA7052 is used
as an output device in this telephone
amplifier. This 1-watt bridge-mode
amplifier has a low quiescent current
and is thus suitable for battery opera-
tion. It is powered from the same sup-
ply as optocoupler IC2. Bridge-mode
amplifiers have the advantage, when
used with a single (asymmetrical) sup-
ply, that they can be connected to the
loudspeaker without coupling capaci-
tors; here, however, we go so far as to
fit two such capacitors — and for a
good reason!
The electrolytic capacitors form a high-
pass filter with a corner frequency of
slightly less than 100 Hz, thus remov-
ing the lowest frequencies. In theory
the corner frequency when using an
8 Q loudspeaker is 85 Hz, but this
value depends, of course, on the
impedance of the loudspeaker. In prin-
ciple a single electrolytic would work
Figure 3. The printed circuit board for the telephone amplifier has two ground planes with a
minimum separation of 6 mm between them.
[ COMPONENTS LIST
Resistors:
R1 ,R3 = lOkD
R2 = QkQ2
R4 = 1 00 kD
R5,R6,R1 1 = lkft
R7 = 220Q
R8,R1 2 = 3kQ3
R9 = 2Q2
R10 = 2kQ2
PI = 250kD preset H
P2 = 10kf2 logarithmic potentiometer,
mono
Capacitors:
Cl = 2|jF2 63 radial
C2 = 1 5nF 400V
C3 = 1 nF 400V
C4 = 68pF
C5,C1 6,C1 8 = 1 OfjF 63V radial
C6,C1 0,C1 5,C1 7 = lOOnF
C7 = 220pF 16V radial (max. diameter
8mm)
C8 = 1 nF ceramic (5mm lead pitch)
C9 = 330nF
Cl 1,012,013 = 470|jF 1 6V radial
(max. diameter 8mm)
Cl 4 = 3nF3 (5mm lead pitch)
Semiconductors:
D1 ,D2 = BAT85
D3 = LED, low current
D4 = 1 N4002
IC1 = LF356
IC2,IC3 = 6N138 (Farnell # 325-831)
IC4 = TDA7052
IC5 = NMV0512SA, C&D
Technologies/Newport Components
(Farnell # 589-822)
IC6 = 7806
Miscellaneous:
K1,K2 = RJ45 socket
LSI = 8D / 1 W miniature loudspeaker
Solder pins
PCB, order code 030379-1 (see
Readers Services page)
3/2006 - elektor electronics
65
HANDS-ON
EAVESDROPPING
Optocoupler tolerances
Optocouplers have wide tolerances. If possible, use a type 6N138
with a current transfer ratio (CTR) of between 250 % and 450 %, as
otherwise IC2 and IC3 may attenuate the signal too much. If the volt-
age across R8 is a few tenths of a volt too low (a tolerance of 1 0 %
is allowable), its value can be increased to raise the voltage, and vice
versa. The circuit is so simple that if necessary other standard opto-
couplers with a Darlington output, such as the IL300, can be used
with a suitable adjustment to the resistor value. The CTR of IC2 is
easy to calculate: CTR = (U R8 /R8) / (Ur^/R 6). Changing R8 naturally
affects the gain of the circuit, although for reasonable adjustments
this should not cause any problems.
just as well, but here the required
capacitance is obtained using two
capacitors in order to prevent a DC
level appearing on the line output,
which is taken from one of the ampli-
fier’s outputs. Because of this, the gain
at the line output is only 33 dB. RIO
ensures that the two electrolytics
remain charged so that there is no
‘click’ when an external amplifier is
connected to the line output. Rll
makes the output short-circuit-proof,
and C14 provides additional filtering to
remove high-frequency interference. To
prevent undesirable coupling through
the power supply connections, the
optocouplers and the amplifier are sep-
arately smoothed (by R7 and C7, and
R9, CIO and Cll respectively).
Power supply
There is little point in galvanically iso-
lating the telephone line from the audio
electronics if their power supplies are
not also kept separate. To this end we
use a NMV05125SA DC-DC converter
which converts an input voltage of 6 V
to an output voltage of 15 V while pro-
viding galvanic isolation up to 3 kV.
The input voltage is a little higher than
the maximum value of 5.5 V specified
in the data sheet, but is clearly within
the ‘absolute maximum rating’ of 7 V.
In practice, it works well, and thanks
to the low load, the output voltage is
slightly higher than the 14.4 V that one
would expect with an input voltage of
6 V. The converter presents a rather
aggressive load to the fixed voltage
regulator, resulting in an output ripple
voltage of 0.1 V pp . According to the
manufacturer’s data, the converter
switches at a frequency of approxi-
mately 120 kHz. However, in our labora-
tory prototype the frequency appeared
to be a little higher: we measured the
ripple frequency to be approximately
300 kHz. This does not affect the per-
formance of the telephone amplifier,
but it does simplify the measures we
need to take in the circuit to suppress
interference.
The fixed voltage regulator is the com-
mon-or-garden 7806, with its input pro-
tected from reverse polarity connection
by a diode. The regulator has a drop-
out voltage of 3 V, and so the input
voltage obtained from a mains adaptor
must be at least 9 V. Of course, the
telephone amplifier can also be pow-
ered from a battery, although the cur-
rent consumption is quite high. We
measured a quiescent current con-
sumption of 72 mA on the prototype
(even using a low current LED for
power indicator D3), with peak current
up to 0.4 A (using an 8 Q loudspeaker);
battery operation is thus only appropri-
ate if the device is to be used occasion-
ally. In any case, a PP3-style battery
will not last long, and it would be bet-
ter to use four AA cells with IC6
replaced by a wire link and D4 ideally
replaced by a Schottky diode such as
the 1N5822 (40 V, 3 A). At 0.4 A this
Schottky diode drops only 0.3 V, con-
siderably less than the 0.8 V drop of a
1N4002.
Keep your distance
The steps we have taken to achieve
galvanic isolation are clear in the
printed circuit board layout of Figure 3.
As can be seen, the ground planes for
the telephone and audio parts of the
circuit are separated. Populating the
board should present no difficulties. Do
not forget the wire links (the circuit
will work without them, but will be
more susceptible to interference).
Sockets should be used for the ampli-
fiers but not for the optocouplers, so
that the isolation voltage is not com-
promised.
The connection points for the external
components (potentiometer, line
socket, loudspeaker and power supply
socket) lie around the edge of the
board and should be fitted with termi-
nal pins.
The circuit can be built into an ordi-
nary plastic enclosure, but a metallic
screen (a piece of tin or unetched
printed circuit board) should be fitted
directly under the printed circuit board,
taking care not to cause a short circuit.
The screen should be connected to the
metal enclosure of potentiometer P2
and to ground. P2 should be fitted as
close as possible to its connection
points on the board, and its connection
wires twisted.
For best audio results a small, good-
quality loudspeaker should be used
inside a large enclosure rather than in
the electronics box, with the loud-
speaker being located a few metres
away from the telephone to prevent
feedback. Alternatively, the line output
can be connected to a hi-fi system.
The circuit discussed in this article is
not approved for connection to the
public switched telephone network
(PSTN) in the United Kingdom.
( 030379 - 1 )
66
elektor electronics - 3/2006
Elektor Electronics (Publishing)
Regus Brentford • 1000 Great West Road
Brentford TW8 9HH • United Kingdom
Telephone +44 (0) 208 261 4509
Fax +44 (0) 208 261 4447
Order now using the Order Form Email: sales@elektor-electronics.co.uk
in the Readers Services section in this issue.
Step into the fascinating world of microcontrollers
Microcontroller Basics
Burkhard Kainka
Microcontrollers have become an indispensable part of modern
electronics. They make things possible that vastly exceed what
could be done previously.
Innumerable applications show that almost nothing is impossible.
There’s thus every reason to learn more about them, but that
raises the question of where to find a good introduction to this
fascinating technology. The answer is easy: this Microcontroller
Basics book, combined with the 89S8252 Flash Board project
published by Elektor Electronics. This book clearly explains the
technology using various microcontroller circuits and programs
written in several different programming languages. In the course
of the book, the reader gradually develops increased competence
in converting his or her ideas into microcontroller circuitry.
ISBN 0-905705-67-X
Flash Microcontroller
Starter Kit
Elektor Hardware & Software
Step into the fascinating world of microcontrollers with
the Elektor Electronics Flash Microcontroller Starter Kit.
Order now the ready-assembled PCB incl. software, cable,
adapter & related articles.
Contents of Starter Kit:
• 89S8252 Flash Microcontroller board
(ready-assembled and tested PCB)
• 300-mA mains adapter
• Serial cable for COM port
• Software bundle on CD-ROM
• Article compilation on CD-ROM
230 Pages
£18.70 / US$ 33.70
£69.00 /US$112.50
More information on www.elektor-electronics.co.uk
KNOW-HOW
MOTORS
and their modern applications
Dr. Thomas Scherer
A linear motor is simply one which produces motion in a straight line rather than in a cir-
cle. We give an overview of the technology and its applications, including examples of
genuine' linear motors and related devices.
Although space does not permit a full introduction to
electromagnetic theory in this article, we should men-
tion that there are linear drive systems where electricity
is turned into motion in a straight line which we never-
theless do not count as genuine linear motors'. These
are so-called dynamic actuators which operate on a
very simple principle using a magnet and a coil, and
which have long been used in various applications.
A good example of this type of drive is the classical
dynamic loudspeaker. Figure 1 is a diagram of its
construction. Its operation is simple and well known: a
coil in a magnetic field experiences a force propor-
tional to the current flowing in it. Apart from applica-
tions in sound production, this principle has been in use
for almost 20 years in the positioning mechanisms for
read/write heads in hard disk drives. Once capacities
exceeded 40 Mbyte and track widths shrank, a more
precise head drive mechanism was required than the
rotary stepper motor design like that used in floppy disk
drives. Under control of specially-designed position sen-
sors, the 'voice coil' mechanism, as it is known,
achieves previously unattainable tracking precision
and, thanks to the high force available, fast seek times.
In machine tools actuators are starting to be used for
simple and short linear motions, replacing pneumatic
systems. In these, the roles of coil and magnet are
reversed: the coil is fixed and the magnet or piece of
metal moves. In contrast to pseudo-linear actuators,
where the linear motion is derived from the rotation of a
conventional electric motor using a rack and pinion or
a belt drive, these solutions have the advantage of
being smaller and simpler.
Further advantages include less wear and tear, high
power and consequent ease of use and reliability. Since
68
elektor electronics - 3/2006
pseudo-linear motors are cheap to produce and can act
over greater distances, they will still have their applica-
tions in machine tools.
Genuine linear motors
A genuine linear motor differs from its rotary cousins sim-
ply in that the stator (the outer cage within which the
rotor turns) is flattened out. The rotor then becomes an
object which moves along the stator rails or which
encloses the one-dimensional stator. Since the translatory
motion in a particular direction is produced without the
use of rack and pinion mechanisms or the like, this kind
of drive is often simply referred to as 'direct drive'.
Therein lies the chief advantage: with many fewer mov-
ing parts there is much less wear and tear and practically
no play in the mechanism. This all leads to very high reli-
ability.
It is interesting to note that the principle has been known
for over 150 years, although industrial use has only
been widespread for the last 30 years or so. This is
because the great position sensing precision required for
machine tools, in the micrometre range, has only recently
become achievable using specially-designed semiconduc-
tor sensors and high-speed electronic motor controllers.
The enormous power available (accelerations of 20 g
and more can realistically be achieved in practice) make
linear motors a good choice more generally, where rota-
tional motion is not needed.
In theory all the principles employed in rotary electric
motors, including stepper motors and three-phase
machines, can be applied to linear motors. And, depend-
ing on the application, these motors can be bought off-
the-shelf in a range of power output levels, maximum dis-
placements and physical constructions. This includes vari-
ants with stationary or moving windings, with permanent
magnets or electromagnets, and exotic designs for spe-
cial applications.
Rail guns and catapults
Few technological advances escape application to
destructive ends, and linear electromagnetic drives are
no exception. Figure 2 shows a schematic diagram of a
gun-like device which, because of its construction, is
known as a 'rail gun'. A conductive projectile slides
between two copper rails and experiences acceleration
when a current flows. During the second world war Ger-
many tried (without success) to construct weapons using
this very straightforward principle. Fortunately such
weapons are not widely used even today, because of the
extremely high currents (thousands or millions of Amps)
involved and the great forces that the components of the
weapon must withstand.
Using a electromagnetically-propelled projectile as a
large-scale catapult is an area of military research. In
principle, a catapult would be an ideal way of launching
a high-speed aircraft using a scramjet engine. Scramjet
engines only start to operate when a relatively high mini-
mum speed is exceeded, rather more than the speed of
sound. Experiments to date using working prototypes use
a supplementary rocket engine, or the prototype is piggy-
backed on a conventional military aircraft and taken to a
great height: it is then allowed to fall until it reaches the
required speed for the engine to start. With scramjets
capable of a speed of up to Mach 1 5, it is technically
reasonable to use a catapult to accelerate them up to sev-
eral times the speed of sound and start them. It is at least
iiroci
rnurjnel
Figure 1.
Principle of the dynamic
loudspeaker. This type
of drive is used in
actuators in industrial
applications.
magnetic
field
curreni
flow
Ff[?jfiorile
Ldf&fii
lores
magnei;c
fi^Jd
Figure 2.
The 'drive' in a rail gun
is very simple. Two
current-carrying rails
and a conducting
projectile are all that is
required.
Figure 3.
The linear motor in a
catapult. Propulsion
and guidance coils
allow a metal saddle to
be accelerated and keep
it on its track. (Source:
Schwandt Infographics)
theoretically possible to achieve this using high-powered
linear motors (Figure 3). NASA has already produced a
number of small-scale working research models, spon-
sored by the military. The system is still, however, science
fiction, since the forces cannot be properly controlled, it
is extremely expensive and humans are not capable of
surviving the necessary accelerations unharmed if the cat-
apult track is short (less than 10 km in length). Practical
applications of linear motors to the transport of human
beings are taking a different course.
The Transrapid
Relatively high speed trains can be constructed using con-
ventional rotary motors and wheels on rails: the Japanese
Shinkansen bullet trains, the German ICE and the French
TGV can reach speeds of over 300 km/h. At higher
speeds special track must be laid and wear and tear
from friction become significant. An experimental version
of the TGV in 1 990 reached an incredible 5 1 5.3 km/h,
3/2006 - elektor electronics
69
KNOW-HOW
MOTORS
Figure 4.
Propulsion and
guidance system of the
Transrapid train in cut-
away view. (Source:
Siemens AG)
although at these speeds the overhead wires and pan-
tographs required maintenance after just this one journey.
Magnetic levitation railways experience no wear and
tear due to friction and it is natural to propel a magneti-
cally-levitated train using a linear motor. Practical ver-
sions of this idea are the Japanese JR-Maglev and the
German Transrapid. Decades of research have gone into
both systems. The Transrapid has been in regular opera-
tion in Shanghai for almost two years and has already
transported over a million passengers over its 30 km
route at some 430 km/h. Both systems are designed for
practical use at around 500 km/h and in principle could
be run even faster. Consideration is being given to
installing a stretch of Transrapid track in the Netherlands
(see http://www.magneetzweefbaan.nl/ magneetzweef-
baan/Default.asp?p=l 7); in Germany there is still only a
prototype track at Emsland in Lower Saxony.
Levitation technology
In the Transrapid design levitation and propulsion are
combined. Figure 4 shows a cross-section of the track
and levitation/propulsion system of the train. On the left
and right of the track there are metal plates upon which
the guidance electromagnets act. The electromagnets
Figure 5.
Under the covers of the
propulsion and guidance
system of the
Transrapid train.
(Source: Siemens AG)
responsible for lifting the train act on the laminations
which form the flat stator built into the underside of the
track on the left and on the right. The air-gap, electroni-
cally controlled from within the train itself, is just 10 mm.
The windings responsible for propulsion are incorporated
into the laminations, made of an isolated aluminium
cable with a cross-sectional area of some 300 mm 2 . The
whole thing functions in the same way as a three-phase
synchronous motor laid flat. A travelling magnetic field is
induced in the windings in the track. If there is a current
in the lifting magnets, they, and hence the train, are lifted
up. Since the train envelops the track, it is practically
impossible for it to become derailed. Figure 5 shows a
view of the actual construction with the covers removed.
Each train or carriage is independently levitated and pro-
pelled by the track. There is thus no separate locomotive
to pull or push the train. The speed of the train is directly
related to the frequency of the alternating currents sup-
plied to the windings, reaching 300 Hz for a speed of
approximately 550 km/h in the case of the Transrapid.
It is worth asking how the 1 0 mm air gap can be main-
tained at these speeds. The gap is inductively measured
thousands of times per second by each segment of the
train and the currents in the guidance and levitation elec-
tromagnets correspondingly regulated. Taking into
account the mass of the carriage a practical control fre-
quency is around 30 Hz. To levitate one segment of the
train and guide it around a curve of track requires an
electrical power of between 55 kW and 1 1 0 kW,
depending on load. The necessary energy comes from a
suitably-dimensioned battery which is capable of main-
taining levitation for approximately one hour if power is
lost. If the battery becomes discharged the train lowers
itself onto runners. The battery is inductively charged
from harmonics of the magnetic propulsion field when the
train is travelling at over 100 km/h.
A train composed of three segments requires a drive
power of up to 45 MV A at a speed of 500 km/h. So that
the whole track is not always powered, it is divided into
many short sections selectively driven by inverters placed
along the track. The inverters are constructed using
power semiconductors such as GTO (gate turn-off) thyris-
tors and IGBTs (insulated gate bipolar transistors) operat-
ing at voltages of over 4000 kV and currents of over
1 kA each. The inverter stations control both frequency
and voltage and receive commands from a central con-
trol station for the track. The Transrapid therefore does
not require a driver on the train.
The modern traveller will naturally be concerned as to
whether his laptop will operate correctly or whether the
data on the magnetic stripe on his credit-card will survive
in the neighbourhood of such high-energy magnetic
fields. Since the air gap is relatively small at 1 0 mm the
stray magnetic fields are kept to a minimum and the field
inside the passenger compartments is comparable in
magnitude to the natural magnetic field of the earth.
Things are rather different in the case of the Japanese JR-
Maglev system where the train rides on a repelling mag-
netic field. This demands a greater air gap in the region
of 1 0 cm, creating stray fields up to a thousand times
greater than those of the Transrapid.
Of course, we have not been able to cover all the details
of the systems here. More in-depth information can be
found by searching the Internet using keywords such as
linear motor', 'rail gun', 'scramjet', 'transrapid' and
'maglev'. Wikipedia also has a considerable amount of
useful information.
( 050374 - 1 )
70
elektor electronics - 3/2006
B mfLtlli
E-blocks Easy Internet Kit
Connect your blocks to the internet
E-blocks are small self-contained electronic
E-blocks Easy CAN Kit
A complex system made transparent
The CAN bus is a resilient, high data rate bus for
communicating between electronic devices in
situations where high data reliability is required.
One use of the CAN bus is in the automotive
circuits and printed circuit boards that can * * .
be combined to create functioning electronic /W _ L- . ~ jS
applications and systems. With the E-blocks In-
ternet board you can connect your own system
to the Internet. This module is perfect to quickly
addasimplewebpagetoyourembedded system. Thisthen permits (measu-
rement) data to be inspected remotely. Applications include reading out a
weather station, switching lighting systems and monitoring and controlling
machines! The application area is truly spectacular!
industry where it is being used as a substitute for
copper wiring looms in cars. The E-blocks Easy
CAN Kit allows you to employ this professional bus system in your own
applications. Implementing CAN is a complex task in languages like C,
but doing so with Flowcode and E-blocks is actually very simple. As a
special offer to encourage you to investigate CAN we are making available
an E-blocks Easy CAN kit at 30% discount. An offer you CAN’t resist!
E-blocks Easy Internet Kit:
Flowcode Professional
£118.00
E-blocks LED board
£ 14.65
E-blocks LCD board
£ 19.30
E-blocks USB Multiprogrammer
£ 77.30
E-blocks switch board
£ 14.65
E-blocks internet board
£ 71.95
PIC16F877
£ 10.50
Ethernet ‘crossover’ cable
£ 5.30
Total value:
£331.65
Special Offer: \ 30 % L
/ d\sco«°y>
£ 232.50
E-blocks Easy CAN Kit:
Flowcode Professional
£118.00
E-blocks LED board
£ 14.65
2 x E-blocks LCD board
£ 38.60
2 x E-block USB Multiprogrammer
£154.60
E-blocks Switch board
£ 14.65
2 x E-blocks CAN board
£ 67.00
2 x PIC16F877
£ 21.00
Total value:
V
£428.50
\
Special Offer:
/
\ 30 °/° L
d\sc° u ”>>
Ordering
Use the order form at the back or go to www.elektor-electronics.co.uk
E-blocks will be shipped after receipt of payment.
Prices are exclusive of postage.
Learn more about E-blocks?
For more information, visit www.elektor-electronics.co.uk/eblocks
HANDS-ON
DESIGN TIPS
Energy recovery
+U B
(±>
RE1
D1
ED X
S ? NAL Ri ✓TV 1
< 2 >
050310-11
Peter Lay
Energy is becoming more and
more expensive, and so we are
always on the lookout for ways to
save energy in circuits. The
author has decided to look at
how to recovery energy from a
relay switching circuit.
If a relay is driven by a transistor
switching stage it is usual to con-
nect a flywheel diode in parallel
with the coil to short out the back
EMF produced when the relay
2
+u B
RE1
[±]
®
050310-12
+u B
current is switched off (Fig-
ure 1). If an LED is wired in
series with the flywheel diode
(Figure 2) it will flash every time
there is an inductive spike with
the transistor turns off. The dura-
tion and brightness of the flash
(and indeed, whether the spike is
large enough to destroy the LED!)
depend on the rate of change of
the current in the relay coil and its
inductance:
Uj = -L di / dt
So far we have not actually recov-
ered any energy. Figure 3
shows a theoretical design where
the energy stored in the relay coil
is recovered so that it can be
used to supply a (low-power) cir-
cuit. The greater the inductance
of the coil and the more fre-
quently it is switched, the more
energy is stored in capacitor C.
The zener diode (in series with
the flywheel diode) limits the max-
imum voltage to which the capac-
itor can be charged. Measured
relative to ground the open-circuit
voltage at point A is the sum of
the capacitor voltage due to the
recovered energy and the supply
voltage. In particular, the voltage
at point A is higher than the sup-
ply voltage.
The author would be interested in
discussing these ideas further with
readers. His e-mail address is
info@peterlay.de.
( 050310 - 1 )
FBI siren with flashing light
Arthur Schilp
This ultra-simple circuit will pro-
duce the familiar sound of sirens
used by US police cars on emer-
gency calls. A small lamp will
also flash synchronously with the
siren sound. The circuit is capa-
ble of powering loads greater
than 1 A for one or more lamps
or a powerful loudspeaker, the kit
producing quite a bit of noise
and light.
The circuit is built from two
astable multivibrators, in this case
the familiar 555 of which two are
present in an NE556 case. Of
course, you are free to use two
555s if that suits you better. Both
timer ICs are configured to oper-
ate as astable multivibrators.
The first timer is configured with
R 1 , R2 and C2 to supply a rec-
tangular signal of about 2 Hz at
pin 9. The lamp is switched on
and off by way of power transis-
tor T1 . The second
555 is configured
using R4, R5 and
C5, and supplies a
square wave at
pin 5 that drives the
loudspeaker. The
toggling voltage at
the output of the first
timer (pin 9) causes
electrolytic capacitor
C3 to be partly
charged and dis-
charged, periodi-
cally, via resistor R3.
C3 is connected to
the control input of
the second timer
(pin 3), causing it to
work as a VCO
(voltage controlled
amplifier). The
upshot is that the fre-
quency of the
square wave applied to the loud-
speaker rises and falls periodi-
cally, rendering a good imitation
of the wailing sound of the US
police car siren (we hear too
often in movies).
The small number of dead-stan-
dard components used enables
this circuit to be built on Ver-
oboard without problems.
( 050349 - 1 )
72
elektor electronics - 3/2006
Energy saver for relays
Klemens Viernickel
When dealing with relays we dis-
tinguish between the pull-in volt-
age and the hold voltage.
Depending on the type of device,
the latter is from about 1 0 % to
50 % lower than the former. This
means that once we have safely
pulled in the relay armature we
can drop the coil voltage to its
hold value, thus reducing the
power dissipated. The simple cir-
cuit shown here does just that: it
consists of a parallel combination
of an LED, an electrolytic capaci-
tor and a resistor, together placed
in series with the relay coil. As
well as saving energy by reduc-
ing the operating current of the
relay and increasing its operating
life the circuit also has the advan-
tage of providing a status indica-
tor in the form of the LED.
The author has used this circuit
with practically all types of relay,
with various rated currents and
voltages. The recommended com-
ponent values are as follows:
• The electrolytic capacitor
should have a value between
100 |jF and 1000 |jF with a
working voltage of 6.3 V,
depending on the rated current of
the relay coil.
• The resistor value should be
between 1 0 Q and 1 k£2 so that
in the active state a current of
20 mA flows through the LED.
• A standard green or yellow
LED with a rated forward current
of 20 mA should be used. When
using relays with a very low coil
current low-current LEDs may be
substituted. Add a zener diode in
series for higher coil voltages
such as 24 V or 48 V.
( 050201 - 1 )
Opamp with increased output current
Klemens Viernickel
Integrated opamps offer advan-
tages such as ease of use, good
price-performance ratio and
small physical size. However,
they seldom have an output cur-
rent drive capability of greater
than about 12 mA, and so they
are not suitable for use in 20 mA
current loop applications, for
example. One solution is to add
a driver stage with the necessary
output power, comprising per-
haps two to four transistors and a
number of other components.
This design takes up board
space and is relatively expen-
sive, tending to offset the advan-
tages of the integrated device.
An alternative possibility is to
boost the output drive capability
by connecting opamps in paral-
lel. The output current will then
be approximately proportional
to the number of opamps.
Instead of a single opamp a
dual or quad device is used to
achieve greater output power.
The idea is shown in Figure 1 . The
output of the first opamp is con-
nected to the input of a further non-
inverting opamp stage as well as
being connected to the output of the
circuit via a resistor. The first opamp
thus drives the second non-inverting
amplifier which provides all the out-
put current of the circuit as long as
that remains within its normal capa-
bility. As the output current demand
increases the second opamp will
reach the limit of its drive capabil-
ity. Its gain will then fall off and a
voltage difference will develop
across its inputs. The first opamp
will then start to deliver more and
more current to the output via the
resistor, and the sum of the output
currents of the two opamps thus
flows through load resistor R[.
By adding another resistor we can
compare the current contributions
from the two opamps (Figure 2).
The complete circuit with two
opamps is shown in Figure 3.
The principle of the circuit can be
extended to more opamps with
their output currents being added
together (see Figure 4).
( 050201 - 2 )
3/2006 - elektor electronics
73
INFO & MARKET
E-CAD DVD
Larry Kossek
CAD Software
for electronics
Schematics,
PCB Design,
Simulation
We recently featured a readership survey on
our website to invite feedback on the DVD
which accompanied the November issue
of Elektor Electronics. This free DVD
was a new departure for us and we
were very grateful for both the posi-
tive and negative comments which
landed on our (virtual) doormat...
Enthalt Info- bzw.
Lehrprogramme
Elektor
lektuur
© 2005 Segment B.V.
In November
2005 we included a
free DVD with a collection of programs for circuit capture
and PCB development/layout along with our magazine.
We were keen to gauge your opinion so a readership
survey appeared for a few weeks on our website at
www.elektor-electronics.co.uk.
On the positive side
without additional expense. The relative merits of the
different programs can be more easily judged to deter-
mine which is more suitable".
The selection of programs was also well received "The
DVD provided me with a good selection of the software
available without the need for lengthy downloads over
the Internet (not much fun for a 15 MB program with any-
thing less than broadband]" .
Students on the whole gave an enthusiastic response and
even some lecturers commented that "the DVD contained
some tools which we could incorporate on some of our
courses at College and University".
The inclusion of KiCAD was appreciated; it has many fol-
lowers and can run in either a Windows or Linux environ-
ment. Apple users were also surprised to find something
for them on the disk: " Excellent , there's even a Mac pro-
gram on there!"
Comments ranging from " Excellent initiative, many
thanks" to "Thanks very much , I'm a new user , very inter-
esting" indicated that many of you thought the DVD was
a good idea. Appreciative readers also responded: "This
compilation has saved me many hours of work" or "Now
I have a complete collection of the programs on one
disk"
Although duly announced on our website and in the
October 2005 issue, the DVD give-away came as a com-
plete surprise to many readers. The disk was praised for
containing "a good cross section of the tools available".
Several readers commented that they had bought the
November issue just for the DVD: "The DVD alone was
worth the cost of the magazine. It has allowed me to
make a practical comparison of the available software
Whether the opportunity to compare many different pro-
grams actually led to users switching to a different pro-
gram package is uncertain. Many comments were along
the lines of: "Interesting and informative but I will con-
tinue to use the program that I am familiar with. Using
other programs only causes a lot of confusion. I am sure
that better software is available but I prefer to stick with
what I know".
One reader mentioned that he had tried out an idea for
a front panel design using Frontdesigner from Abacom
and liked the result so much that he went ahead and
purchased the program immediately after using it for the
first time.
74
elektor electronics - 3/2006
Eagle
No Responses
SPIan & SPrintLayout
Target 3001!
OrCAD
Proteus
KiCAD
Layo PCB
Design Suite
Table 1
The Eagle has landed
Of all the software on the DVD Eagle was, on average
voted the most popular across all four language web-
sites. The UK response shows an anomalous preference
for KiCAD but this was probably due to enthusiastic
KiCAD fans having teamed up to push the survey results
in a certain direction.
The overall results are collected together in Table 1 .
What is not shown on the table is the interest expressed
by our readers in so many different programs.
Here we can ascertain that around 60 % of the UK read-
ership indicated that their favourite program was for pri-
vate use. It was also noted that the software used at home
was not always the same software as that used at work.
When choosing a program the software costs were con-
sidered to be an important factor but not as influential as
the opinions of colleagues and friends who were familiar
with the software. The simplicity of the user interface is
also an important factor; the faster you can begin getting
results with a program the more you tend to like it.
The majority of respondents were satisfied or more than
satisfied with the programs they were using. Some 1 0 to
1 8 % thought that there was probably a better solution
that they had not yet found. These readers were particu-
larly grateful for the free DVD in the November issue.
Suggestions and comments
It was clear from the start that we wouldn't be able to pro-
vide a copy of every available layout program on our
DVD. Many of you suggested Altium - Protel, Auto-
TRAX EDA, DipTrace, DouglasCAD, Express PCB,
PADS, SupermaxEGAD, TINA simulator and Vir-
tual Breadboard etc. As reported in Mailbox, a number
of CAD software manufacturers simply declined our offer
to have a demo or trial version of their product included in
the DVD. One reader would have liked a copy of Scooter
while another would have appreciated comments about
the 100-euro version of BAE. Circuit simulation software
was not included on the DVD but an overview of the topic
may be the subject of a future DVD...
Other respondents commented that they were not aware
of the existence of some of the programs and were grate-
ful for a chance to try them out.
One parent suggested that it may have been useful to
include some simple PCB layout tools that could be used
by, say, a 1 2 year old. This excellent suggestion has
niLj flnucnn
n - jfl&c-
U 5P.JU1 A r.P'm waul
QTfl'Uffl KMr
■OtGAD
nrwv.niK
HHCAC
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Figure 1.
Program popularity
amongst the four
European Elektor
Electronics websites.
0%
50%
100 %
□ Hobby
■ Pro
□ Mo
resp
Figure 2.
User profile
3/2006 - elektor electronics
75
INFO & MARKET
E-CAD DVD
been noted and will no doubt be considered when we
next get the opportunity to make similar offers.
A KiCAD enthusiast has suggested that we run a tutorial
series on this software, good idea, any volunteers out
there willing to take this on?
Some programs received critical remarks, the latest offer-
ing from Protel for example attracted a number of nega-
tive comments while another reader observed that:
"Boordmaker Win is far too expensive for private use!!”
It came as no surprise that the most popular programs
attracted praise (e.g. EASY PC), and especially SPlan
and Sprint Layout were often mentioned.
"SprintLoyout fulfils my requirements more precisely than
any of the other programs ".
One reader suggested that a future DVD might feature
PC-based test equipment and circuit simulation software.
Another reader thought a DVD containing programming
tools and program development environments would be
useful. These suggestions have been noted and may be
incorporated in future DVDs.
Some readers commented that most of the programs are
demo versions so it is difficult to make a meaningful com-
parison between the software especially if you are not
aware of the price of the full software package: "it would
not be fair to compare a 200 pound program with a
10,000 pound without taking into account the price of
the software. "
We would beg to disagree on this point and suggest that
program comparisons are more likely to be 'objective' if
the cost of the software is not considered. However we
take on board that it may have been useful to include a
table indicating price / demo / freeware information.
You can't please everyone...
Negative reactions were also registered, some readers
complained that the DVD was missing from their issue
and these have hopefully been supplied free of charge
from the publishers by now.
Some readers reported that they could not run the DVD.
Many of the problems turned out to be "user induced"
ranging from surprise when their CD-ROM drive was
unable to run the DVD (I must admit I fell into this trap
when I tried to run the DVD at home on my ancient lap-
top) to "/ can't see anything on the TV when I plug the
disk into my DVD player” a mistake which can probably
be attributed to the effect on the brain of too much party-
ing in the run up to Christmas.
Disks damaged in transit were quite rare and have been
replaced.
Some of the more extreme reactions included comments
that the DVD was "completely unnecessary " or "totally
useless ". Other comments judged the disk contents to be
"meagre”.
One problem that we cannot be held responsible for is a
symptom of the well known "Windows disease". It is pos-
sibly one of the most frustrating features of some Win-
dows programs that after trialling software and subse-
quent de-installation, traces of the original program can
still be found on the computer and are notoriously difficult
to remove. This is however not the case for all programs,
some are more well behaved than others.
A number of you would have liked to see a more
detailed article accompanying the disk: "It was disap-
pointing that the comparisons were sketchy and inade-
quate, but nevertheless it was a splendid effort
regardless " Another commented: "many of the programs
require a large investment of time and the limited nature
of the demo software means that it was not worth the
time and effort." Reading between the lines it seemed
that many respondents were looking for advice on
the best system to purchase, but such recommenda-
tions were not what we intended and are anyway
almost impossible to make for this type of software.
Many had hoped for fuller versions of the software but
we can only pass on the version which is supplied to us.
It will only take one publisher to release a freeware ver-
sion with more features for the others to follow suit to
maintain market share.
A tale of woe
Quote: "/ have been using the program Capture and
Layout for a number of years and from day one I
have been looking forward to the next software
release that would surely improve the program.
Unfortunately it has not been such a simple proce-
dure; Features that were good in the previous ver-
sion of the software have been omitted in the latest
version. Known bugs were fixed but it seemed like
just as many new bugs were introduced! Multiple
' undo's' are implemented in Capture 10.0 but only
work for a few, less important commands. In Lay-
out, like previous versions there is only one or no
step forward or back. This problem was identified
in a review of the program in Elektor Electronics
many years ago. This has been my experience with
a CAD program made in the USA."
Who would have thought that PCB layout could be such
a headache?
Taking into account the positive and negative comments it
seems that on the whole the disk was received favourably.
We have gained much from this experience and once
again would like to thank all those who participated.
( 050323 - 1 )
76
elektor electronics - 3/2006
RETRONICS
INFOTAINMENT
Elektor Plotters ( 1 988- 1991)
Jan Buiting
This story starts in May 1988
with the publication of an article
with the delightfully simple and
technically correct title 'Plotter
(part 1 )". The design was based
on a mechanical drawing and
an accompanying letter sent to us
by one J. Arkema from the
Netherlands. This was at a time
that plotters were noisy, slow and
expensive PC adjuncts only seen
in the cellars of professional engi-
neering bureaus running Auto-
CAD or similar programs. Of
course, the electronics hobbyist
had different things in mind to do
with a plotter, if only he could get
his hands on one: drawing
schematics and 'printing' PCB
artwork! Unfortunately, to this
day a working high-end plotter,
particularly one of Hewlett
Packard, is a fairly rare find.
The proposed plotter, then, was a
simple X-Y type, with the Y move-
ment carried out by a platen mov-
ing the paper sheet (up to A2
size!), and the X motion handled
by a pen carriage covering a
span of about 50 cm along a
guide bar. The May 1 988 article
came with a set of mechanical
drawings of the (mostly alu-
minium) parts to cut, mill, drill and
file before you could even start
dreaming of assembling the plot-
ter. These drawings were pro-
duced manually on an ordinary
drawing stand. It turned out a
quite unusual job for our drawing
staff, and it took several versions
before a 'blueprint' was pro-
duced that could be read by
someone accustomed to working
with a lathe. Mind you, no plotter
was available, let alone a pro-
gram or a PC.
Unfortunately, despite the efforts
that went into producing the
drawings, a poor balance was
struck between the mechanical
construction (wrapped up in
about two pages) and the elec-
tronics we all understood so
much better. Although a mechan-
ical parts list was printed and an
artist's impression of the assem-
bled plotter, we were inundated
with questions like 'how to
assemble the thing' and where to
obtain Skiffy parts, Binder mag-
nets, Berger stepper motors and
Rotring pen refills. Fortunately,
one of our advertisers, Meek-it
from The Hague, Holland,
stepped in and offered a kit of
parts to build the plotter.
After al the hubbub around the
mechanical construction, silence
reigned when we published
part 2 of the article in June 1 988.
In it, we duly described the algo-
rithms that (we assumed) would
enable talented readers to write
their own drivers to control the
plotter from a PC. A wrong
assumption, as virtually no
response was received and for
quite some time it seemed that no
one had the fuzziest notion of
what we meant by octants, step-
per motor look-up tables and
MC3479 control bytes, let alone
Bresenham's algorithm.
The silence was broken in March
1 990 when we were finally able
to publish "Plotter Mark 2", dis-
cussing a few mechanical
improvement to the original
design but more importantly a
'partly HPGL compatible' driver
for PCs! The program from B.
Lewetz was called Mondriaan
after the Dutch artist (1877-
1944). Although it supported just
six basic commands from the
much larger HPGL set, the pro-
gram effectively made the project
come alive after a two year wait.
Reader response was overwhelm-
ing as the missing link between
hardware and software had been
catered for at long last. The
famous 'Columbia' and 'nozzle'
drawings were supplied with the
program, along with a few pen
calibration and plotter test files.
Market leading programs like
Autocad and Autosketch at the
time employed only six HPGL
commands so the Elektor plotter
did just fine on the Centronics
port. In the UK, Cliff Gregory
optimised the mechanical design
of the Elektor plotter and started
to supply 'Plotter Mk3' kits com-
prising ball bearings and stainless
steel parts.
Finally, in September 1991 we
published another plotter driver,
this time written in Turbo Pascal
and supporting 17 HPGL com-
mands. Supplied on a 360 kB
5.25 inch floppy disk (and later
on 3.5 inch), it turned out to be
huge sales success.
( 065015 - 1 )
Retronics is a monthly column covering vintage electronics including legendary Elektor designs. Contributions, suggestions and requests are welcomed; please send an
email to editor@elektor-electronics.co.uk, subject: Retronics EE.
3/2006 - elektor electronics
77
SPI BOX
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PUZZLE
INFOTAINMENT
Hexadoku
Puzzle with an electronic touch
Here is the third Hexadoku puzzle, the brain
teaser for electronics fans and their family
members. Solve the puzzle and win one of the
fantastic prizes!
The instructions for the puzzle
are straightforward. In the
diagram composed of 1 6_1 6
boxes, enter numbers in such
a way that all hexadecimal
numbers 0 through F (that's 0-
9 and A-F) occur once in
every row, once in every col-
umn, and in every one of the
4_4 boxes (marked by the
thicker black lines). A number
of clues are given in the puz-
zle and these determine the
start situation.
Your solution may win a prize
and requires only the num-
bers in the grey boxes to be
sent to us (see below). The
puzzle is also available as a
free download from our
website (Magazine — » 2006
— > March).
( 065043 - 1 )
Prize winners
The solution of the January
2006 Hexadoku is: EA639.
The E-blocks Starter Kit
Professional goes to: Ian
Mowatt (Chester).
Entering the competition
Please send the numbers in the grey
boxes by email, fax or post to
Elektor Electronics Hexadoku
Regus Brentford
1 000 Great West Road
Brentford TW8 9HH
United Kingdom.
Fax (+44) (0)208 2614447
Email:
editor@elektor-electronics.co.uk
Subject: hexadoku 03-2006.
The closing date is 27 March 2006.
Competition not open to employees of
Segment b.v., its business partners
and/or associated publishing houses.
An Elektor SHOP
Voucher worth £35.00
goes to: M. Devereux (Stock-
ton on Tees); Paul Ackerman
(Broughton Ashley); Colin
Wilkinson (Wareham).
D
1
A
C
9
4
2
B
8
F
7
5
3
8
0
7
6
2
4
7
6
C
A
0
3
2
4
9
D
6
0
2
2
8
F
4
9
D
E
7
A
6
3
7
B
F
A
D
2
6
9
4
1
4
2
7
8
0
F
A
5
D
7
1
4
D
C
B
0
9
0
B
5
F
1
4
B
2
5
E
1
6
8
9
C
4
2
8
E
5
B
A
9
4
0
2
1
7
D
A
F
6
5
8
7
8
6
9
A
0
F
B
E
A
0
5
9
6
C
Solve Hexadoku
and win!
Correct solutions qualify for
an
E-blocks Starter Kit
Professional
worth £248.55
and three
Elektor Electronics
Shop Vouchers
worth £35 each.
We believe these prizes
should encourage all our
readers to participate!
3/2006 - elektor electronics
79
ELEKTOR
SHOWCASE
To book your showcase space contact Huson International Media
Tel.
(0) 1 932 564999
Fax 0044 (0) 1 932 564998
ALLGOOD TECHNOLOGY
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DESIGN GATEWAY
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USB has never been so simple...
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BETA LAYOUT
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Beta layout Ltd Award-
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COMPUCUT
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EASYSYNC
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EasySync Ltd sells a wide
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ELNEC
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• device programmer
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• universal and dedicated device programmers
• excellent support and after sale support
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FUTURE TECHNOLOGY DEVICES
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FTDI designs and sells
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FUTURLEC
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80
elektor electronics - 3/2006
products and services directory
JLB ELECTRONICS
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Suppliers of electrical / electronic parts and
consumables. Including:
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KMK TECHNOLOGIES Ltd.
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Low Cost DIY Robotic Kits
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LONDON ELECTRONICS COLLEGE
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Leaders in Device
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• Online shop
• Low Cost Adapters for all
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• Single Site and Gang Programmers
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NEW WAVE CONCEPTS
www.new-wave-concepts.com
Software for hobbyists:
• Livewire circuit simulation
software, only £34.99
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software, only £34.99
Available from all Maplin Electronics stores and
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OLD COLONY SOUND LAB
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magazines for the DIY audio enthusiast!
PCB WORLD
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World-class site: Your magazine project or
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VIRTINS TECHNOLOGY
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ELECTRONIC ENTHUSIASTS
Only one magazine tests its projects and circuits in its own lab before publication
ELEKTOR ELECTRONICS
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3/2006 - elektor electronics
81
lektor
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R8C/1 3
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Kits & Modules
Versatile FPGA Module
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R8C/13 microcon-
troller board with SIL mm
pinheaders supplied
separately.
050179-91
£8.30/$ 15.60
OBD-2 Analyser
(July/August 2005)
Kit of parts including PCB, programmed controller, compo-
nents (including IC7 ; IC3 = PCA82C250,
12 V), enclosure and RS232 cable.
OBD cable not included.
050092-71
£52 .50/ $96.95
OBD cable
050092-72
£27.55/ $51 .95
Further products from Elektor Electronics:
READY-BUILT PROJECTS £ $
ClariTy 300-W Class-T Amplifier
030217-91 Amplifier board with SMDs pre-fitted; cores for LI & L2 34-50 55.70
Flash Microcontroller Starter Kit
010208-91 ready-assembled PCB incl. software, cable, adapter & related articles 69-00 112.50
Gameboy Digital Sampling Oscilloscope (GBDSO)
990082-91 ready-assembled board, incl. the PC software and related articles 103-00 183.00
Micro Webserver with MSC1210 Board
030060-91 Microprocessor Board, ready-assembled
044026-91 Network Extension Board, ready-assembled
044026-92 Combined package (030060-91 & 044026-91 & related articles)
LPC210x ARMee Development System
040444-91 Processor board, ready-made and tested
75-90
44-50
117-50
25-50
142.95
83.95
220.95
48.05
NO. 352 MARCH 2006
Application Board for R8C/13
050179-92 Ready-assembled board
48-27
90.94
050179-1 PCB
13-77
25.94
030451-72 LCD with backlight
7.25
13.65
030451-73 Poly-LED display
25.50
48.05
FPGA-Protoyping board
050370-91 Ready aseembled board
Telephone Eavesdropper
030379-1 PCB 9.05 17.05
NO. 350 JANUARY 2006
95-watt Laptop PSU Adaptor
050029-1 PCB
4-80
9.05
Automatic Attic Window Controller
0501 39-1 1 Disk, PIC source & hex code
5-20
9.75
050139-41 PIC16F84A-20I/P, programmed
13-10
24.65
030451-72 LCD Modue 2x16 characters
7-25
13.65
030451-73 PLED Module 2x16 characters
25-50
48.05
SMD Reflow Soldering Oven
05031 9-1 1 Disk, source and hex code
5-20
9.75
050319-41 AT89C52/24JI, programmed
7-60
14.25
030451-72 LCD Modue 2x16 characters
7-25
13.65
030451-73 PLED Module 2x16 characters
25-50
48.05
Timer Switch for Washing Machine
050058-1 PCB
8-90
16.70
050058-1 1 Disk, PIC source & hex code
5-20
9.75
050058-41 PIC16F84, programmed
13-10
24.65
NO. 349 DECEMBER 2005
From A to D via USB
050222-1 PCB
7-95
14.95
050222-41 IOW24-P, programmed
9-40
17.75
Telephone Supervisor
050039-41 PIC1 6F628-20/P, programmed
8-20
15.55
050039-81 CD-ROM, PIC hex & source codes, LCM First Server
6-90
12.95
NO. 348 NOVEMBER 2005
Versatile FPGA Module
040477-91 Ready aseembled plug-on module
For subscribers
171.80 323.50
Remote Control by Mobile Phone
040415-1 PCB
04041 5-1 1 Disk, PIC source & hex files
6-20
5-20
11.65
9.75
INFO & MARKET
SNEAK PREVIEW
SPI Box
Many of today's microcontrollers and associated peripheral ICs sport a Ser-
ial Peripheral Interface (SPI) connection for programming and control pur-
poses. The SPI is a relatively simple add-on and requires little hardware
to drive from a PC. Usually, an RS232 port is 'misused' for the purpose
but admittedly that's fraught with a few disadvantages. The programmer
we've in mind goes round these problems while also ensuring short pro-
gramming times even if a USB/serial adapter is being used for lack of an
RS232 port on the PC or laptop.
Theme Plan for 2006
January Recycling / Reverse Engineering
February Motors / Propulsion
March Development/ Microcontrollers
April Power Supplies / Safety
May Soldering / Etching
June Satellites
July/ August . . . .Summer Circuits
September Esoterics / Test & Measurement
October e-Simulation
November Chipcards / Protection
December Electromechanical / Enclosures
The Electronic Laundry
Microcontrollers are applied in massive numbers in all sorts of consumer-market electrical equipment. Large manufacturers spend
lots of timer and money on hardware and software development for a specific product. Eventually, units have to be mass-pro-
duced by the millions so design errors and bugs are out of the question. We paid a visit to of washing machine giant Miele for a
peek in their hard- and software development department.
Mains Adapters Undressed
Switch-mode versions of the trusty mains adapter (or 'battery eliminator') are
increasingly seen with mobile equipment like PDAs, phones and MP3 players. The
Also... newer versions no longer have bulky, energy wasting mains transformers and lin-
Electric Fence; AA Cell Characteriser; ear regulators. We took a few of these newcomers apart to examine their construc-
FPGA Applications (1 ); E-blocks; tion and operation. The experience so gained is put into practice by the home con-
Hexadoku Puzzle. struction of a DC-DC converter.
RESERVE YOUR COPY NOW! The April 2006 issue goes on sale on Thursday 16 March 2006 (UK distribution only).
UK subscribers will receive tbe magazine a few days before this date. Article titles and magazine contents subject to change.
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January 2006
<D
lectronics
Home Automation
This CD-ROM provides an overview of
what manufacturers offer today in the field
of Home Networking, both wired and wireless.
The CD-ROM contains specifications, standards
and protocols of commercially available bus and network systems.
For developers, there are datasheets of specific components and
various items with application data. End-users and hobbyists will find
ready-made applications that can be used immediately.
The documents included on the CD-ROM have been classified
according to communication media: mains (power line), coaxial cable,
telephone line and wireless (RF).
Index of Advertisers
Allgood Technology, Showcase www.allgoodtechnology.com
ATC Semitec Ltd, Showcase www.atcsemitec.co.uk ....
Audioxpress, Showcase www.audioxpress.com ....
Avit Research, Showcase www.avitresearch.co.uk . . .
.80
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.81
.80
Beta Layout, Showcase www.pcb-pool.com 45, 80
Bitscope Designs www.bitscope.com 15
Breadboarding Systems www.breadboarding.co.uk 11
Burn Technology LTD, Showcase www.burntec.com 80
Compucut, Showcase www.compucutters.com 80
Compulogic, Showcase www.compulogic.co.uk 80
Conford Electronics, Showcase www.confordelec.co.uk 80
Cricklewood www.cricklewoodelectronics.com 45
Danbury, Showcase www.DanburyEiectronics.co.uk
Design Gateway, Showcase www.design-gateway.com . . .
Eaglepics, Showcase www.eaglepics.co.uk
.80
.80
.80
Easysync, Showcase www.easysync.co.uk 7, 80
Elnec, Showcase www.elnec.com 80
Eurocircuits www.thepcbshop.com 33
Future Technology Devices, Showcase . . .www.ftdichip.com 3, 80
Futurlec, Showcase www.futurlec.com 80
Flitex www.hitex.co.uk 27
Ipeva Limited, Showcase www.ipeva.com 80
Jaycar Electronics www.jaycarelectronics.co.uk 2
JLB Electronics, Showcase www.jibeiectronics.com 81
KMK Technologies Ltd, Showcase . . .
Labcenter
Lichfield Electronics
London Electronics College, Showcase
MQP Electronics, Showcase
New Wave Concepts, Showcase
Newbury Electronics
Number One Systems
Nurve Networks
PCB World, Showcase
Pico
Quasar Electronics, Showcase
Robot Electronics, Showcase
Showcase
SK Pang Electronics, Showcase
Sytronic Technology, Showcase
Ultraleds, Showcase
USB Instruments, Showcase
Virtins Technology, Showcase
.www.kmk.com.hk 81
.www.iabcenter.co.uk 88
.www.lichfieldelectronics. co.uk 33
.www.lec.org.uk 81
. www. mgpelectronics. co.uk 81
.www.new-wave-concepts.com 81
. www. ne wburyelectronics. co.uk 33
.www.numberone.com 45
.www.xgamestation.com 33
. www. pcb world, org. uk 81
.www.picotech.com 27
.www.guasarelectronics.com 26, 81
. www. robot-electronics, co.uk 81
80, 81
.www.skpang.co.uk 81
. www. m2mtelemetry. com 81
.www.uitraieds.co.uk 81
.www.usb-instruments.com 81
.www.virtins.com 81
Advertising space for the issue of 11 April 2006
may be reserved not later than 14 March 2006
with Fluson International Media - Cambridge House - Gogmore Lane -
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Fax 01 932 564998 - e-mail: aerrvb@husonmedia.com to whom all
correspondence, copy instructions and artwork should be addressed.
3/2006 - elektor electronics
87
Schematic &
PCB Layout
JLU ! JL J ■ a 1 • I
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New Features
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Interactive Design Rule Check,
Mitring / Unmitring.
Enhanced track editing.
The Complete Electronics Design System
Powerful & flexible schematic capture.
Auto-component placement and rip-up/retry PCB routing.
Polygonal gridless ground planes.
Libraries of over 8000 schematic and 1000 PCB parts.
Bill of materials, DRC reports and much more.
Mixed Mode SPICE Circuit Simulation
• Struct/Array expansion.
• ELF/DWARF file loader.
• Berkeley SPICE3F5 simulator with custom extensions for
true mixed mode and interactive simulation.
• 6 virtual instruments and 14 graph based analysis types.
• 6000 models including TTL, CMOS and PLD digital parts.
• Fully compatible with manufacturers’ SPICE models.
• Expanded model libraries.
Call Now for Upgrade Pricing
Proteus VSM - Co-simulation and debugging for popular Micro-controllers
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Compatible with popular compilers and assemblers from Microchip,
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/* Proto cl on *
/* Sat Port 1,
ISBN 90-5381-159-1
£1 4.95 (US$ 26.50)
Elektor’s Components
Database gives you easy
access to design data for
over 5,000 ICs, more than
35,000 transistors, FETs,
thyristors and triacs, just
under 25,000 diodes and
Elektor Electronics
(Publishing)
Regus Brentford
1 ,800 optocouplers.
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are fully interactive, allowing
1000 Great West Road
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More information on www.elektor-electronics.co.uk
Contents
Foreword
Why C? 4
C Basics
The structure of a C program 6
The main function 6
Comments in C 6
The #include directive 7
Keywords in C 7
Constants and Variables
Number systems 8
Data types 8
Constants 9
Variables 9
Operators in C
Arithmetic operators 1 1
Relational operators 11
Logical operators 1 1
Shortcuts 12
Functions in C
The function concept 13
Declaring a function 13
Calling a function 14
Program Control
If 16
if... else 16
switch 17
for 18
while 19
do. ..while 20
Appendix
Header file sfr_r81 3. h 21
Header file math.h 23
elektor electronics
3
Foreword
Why C?
Many electronics hobbyists have used microcontrollers successfully, and they have
also written wonderful programs in assembly language. As the size and complexity of
an assembly-language program increase, the desire for a more effective
programming environment also increases. Anyone who has tried to implement a
mathematical function in assembly language, such as 1/x, sin(x) or the like, knows
the problems. Here a high-level language such as C, which is the industry standard
in the microcontroller and microprocessor world, offers decisive advantages. C
programs are portable, which means the program structure can be transferred to
other types of microcontrollers after it has been written. The only things that have to
be modified are the port assignments and the settings for the special function
registers.
Professional programmers claim that an assembly-language program that would take
14 days to generate can be generated in 2 to 3 days in C. What’s more, an
increasing number of semiconductor manufacturers are making highly effective
development environments available at no charge. That’s another good reason to
start using C.
But there’s a hitch. As we all know, the gods have ordained that success doesn’t
come without hard work. An introductory course in the C language and sample
programs from technical magazines can help you overcome the initial hurdles, but
will take a while before you can write you own programs. You will also have to master
a certain amount of specialist vocabulary. As can be seen from contributions to
microcontroller forums and questions asked in these forums, that forms a significant
problem for many electronics hobbyists.
This booklet is limited to the basic elements of the C language. We have intentionally
omitted complex C structures such as pointers, arrays, strings, structures, unions and
the like. This booklet is intended to serve as a reference for beginners. It cannot
replace a basic course in C, nor is it intended to do so.
4
elektor electronics
C Basics
The structure of a C program
All C programs consist of several parts, such as comments, preprocessor
instructions, declarations, definitions, expressions, assignments and functions. The
following listing shows a simple example.
/* FILE :my1c.c */
/* DATE :Wed, Nov 23 2005
/* DESCRIPTION Program toggles leds on port_1
/* CPU TYPE :R8C 7
include "sfr r813.h"
compiler directive
long t;
setup_r8c()
{
prcO = 1 ;
cm13 = 1;
cm15 = 1;
cm05 = 0;
cm16 = 0;
cm17 = 0;
cm06 = 0;
asm("nop");
asm("nop");
asm("nop");
asm("nop");
ocd2 = 0;
variable
declaration
function 1
/* Protect ox'C * /
/* Xin Xout 7
/* XCIN-XCOUT drive capacity: HIGH 7
/* Xin on 7
/* Main clock = No Division mode 7
/* CM 16 and CM17 enable 7
/* Waiting for stable oscillation 7
/* Assembly-language code
, . . assembly-language code
pi = 0x0F;
for (t=0; t<1 50000; t++);
value
asskmment
void main
main function
{
}
setup_r8c();
toggle_leds();
elektor electronics
5
The main function
Every C program must include at least one function, which is called the main
function. This is the primary function in a C program, and it is always the first function
to be called when the program is run. It’s considered good programming style to have
the main routine consist primarily or entirely of function calls, instead of containing
the entire code of the program. That makes the program a lot easier to understand
and maintain, and it allows the programming effort to be divided among several
programmers for large projects. The main function is declared in the same manner
as any other function.
void main(void)
{
/* Your program
block j''
main()
/* Your program
markers 1
code goes here 7 l
code goes here 7
}
All instructions and functions belonging to main are enclosed in curly brackets
{...}. This is called ‘block building’. In the above example, void means ‘empty’
and indicates that the main function does not require any input parameters and
does not return any result after the instructions are executed. The two instances of
the void keyword can also be omitted if desired.
Comments in C
All text strings and phrases that don’t form part of the actual program are called
‘comments’. Comments are ignored by the compiler, which means they do not
occupy any space in memory. However, they are quite valuable for explaining the
program (or important parts of the program) to other people. And of course, they’re
very useful for the author of the program as well. In many cases, you may not
remember why you wrote the code in a particular manner when you look at your
program several days later. And no matter how appropriate the saying ‘lean is
keen’ may be in other contexts, it certainly doesn’t apply to computer programs.
/* // This is a single-line comment.
Comments are
enclosed between
diagonal slashes
and asterisks. 7
Single-line comments begin with two diagonal slashes and end automatically at
the end of the line.
A semicolon ( ; ) is usually used to designate a comment in assembly-language
programming, but in the C language it marks the end of an instruction.
6
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#include
There are many declarations and functions that are not included in the ANSI
standard for the C language, even though they may be necessary or very useful.
They are commonly ‘hidden’ in libraries. You have to tell the compiler to include
these library files, which are called ‘header files’, so it can use these declarations
and functions when it compiles your C source code. You can recognise header
files by the .h file extension.
Examples:
#include "stdio.h"
Used in C programs intended to be run on a PC.
[Standard input/output; includes the print function printf() .]
include "sfr_r813.h"
The Renesas library. The names and bits of the registers of the R8C
microcontroller, such as pi , pdl , p1_7 etc., are defined here.
Keywords in C
A total of 32 terms known as ‘keywords’ are defined in the ANSI standard for the C
language. These keywords are reserved for the compiler. All keywords must be
written in lower-case characters, and they are not allowed to be used for other
purposes (such as naming variables).
auto
double
break
else
case
enum
char
extern
const
float
continue
for
default
goto
do
if
int
struct
long
switch
register
typedef
return
union
short
unsigned
signed
void
sizeof
volatile
static
while
Many C compilers add supplementary keywords to those defined in the ANSI
specification in order to make best use of the features of the compiler or
microcontroller. The terms listed below are also designated as keywords for the
R8C family of microcontrollers.
asm asm near
far _Bool restrict
near far inline
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7
Constants and Variables
Number systems
The C language can work with several different number systems (number bases):
decimal, octal, and hexadecimal.
Numbers stated without any special identification (notation) are interpreted as
decimal numbers by default. Numbers in all other number systems must be
specially identified. Octal numbers begin with 0, hexadecimal numbers with Ox,
and binary numbers with Ob.
Base
Notation
Available characters
Example
Decimal(IO)
-
0123456789
5
Octal(8)
0 ...
01234567
05
Hexadecimal(16)
Ox...
01 23456789ABCDEF
0x5
Binary (2)
Ob
0 1
Obi 11 10000
The English (US) convention is always used for numerical notation. That means a
full stop (‘period’) is used as the decimal marker for floating-point numbers. In C,
the comma is used in as a separator in lists of numbers or variables. A colon
marks a range of numbers.
Examples:
3 N 14159
3,4
3 and 4
0:3
0->3, thus 0, 1, 2, and 3
Data types
In C, the type of a variable must be declared before it can be used. Otherwise the
compiler will not know how much memory to allocate for the variable. Basically,
you should always select a type that is adequate for the intended purpose and
requires the least amount of memory space. The most important data types are
listed below.
Type
Memory space Value range
_Bool
8
0 , 1
char
8
0 -> +255
signed char
8
-128 -> +127
int, short
16
-32768 -> +32767
unsigned int
16
0 -> +65535
long
32
-2147483648 -> +2147483647
float
32
-1.17..e-38F-> +3.4..e-38F
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Examples:
_Bool stop_button // button has only two states: on & off
unsigned int _year // 0 -> 65535 sufficient for year numbers
float _volume // floating-point number for calculations
Constants
Constants are numbers that cannot be changed in the program. That also includes
all ‘normal’ numbers. Whole numbers (integers, or int ) are written without a
decimal marker (decimal point). Floating-point numbers (float ) have a decimal
point followed by additional digits. Characters (char ) are enclosed between
single quotation marks ( ' ). Constants are declared using the #define
keyword.
#define <label>
Examples:
value
No ; because this is
only relevant for the
compiler
#define true 1
#define false 0
#define pi 3.14159
#define letter_1 'A'
// 1 = true
// 0 = false
// the factor □
// 'A' key on the keyboard
The names of constants, variables and functions can be freely selected, but
they are not allowed to contain any keywords or operator symbols.
Basically, only the letters of the English alphabet, numerals and the
underscore ( _ ) are used for names. You should chose names that give a
good indication of the practical meaning of the constant. For instance,
alarm_btn is much more meaningful than tl .
Variables
A variable is an item stored in memory that can be changed in the program.
Variables can be numbers, letters, or text strings. In C, all variables must be
declared before they can be used. Variables are considered to be ‘statements’,
which means variable declarations must be terminated with a semicolon ( ; ).
Variables are defined as follows:
type <label>
Examples:
_Bool keypress ;
long counter ;
float radius ;
; because this is a
processor instruction
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9
Variables are assigned values as follows:
<label>
value
Examples:
keypress = 1 ;
keypress = false ;
counter = 100 ;
min_val = counter - 50 ;
max_val = counter * counter ;
_circum = radius * 2 * pi ;
Commands and instructions for the processor, which are called
‘statements’, are terminated with a semicolon ( ; ).
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Operators in C
Arithmetic operators
The symbols for arithmetic operators in C correspond to the familiar symbols used
on pocket calculators:
+ addition
// examples:
y = x + 3 ;
subtraction
//
y = X- b ;
* multiplication
//
_Q
*
CO
II
/ division
II
Y = a/b ;
The equal sign has a different meaning in C than in ordinary mathematics. In C, it
is called the ‘assignment operator’. That means the expression to the right of the
equal sign is computed and the result is assigned to the variable to the left of the
equal sign. The following expressions are thus allowed in C, but not in normal
mathematics:
/ \
!
)r
X = x+y ;
x = -x ;
// compute x + y and store the result in x
// change the sign of the variable x
Relational operators
Relational operators are used to compare variables. They return the result true
or false , depending on the event.
>
greater than
== equal
>=
greater tnan or equal
!= not equal
<
less than
<=
less than or equal
Logical operators
The logical operators AND, OR and NOT can be used to execute the familiar
operations of digital logic.
b a
AND
a && b
a || b
OR
!a
NOT
0
0
0
0
1
0
1
0
1
0
1
0
0
1
1
1
1
1
1
0
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11
Example:
if(_price <= max_price && _account > 1 000)
_buy();
/* The function _buy() will only be called if _price is less
than or equal to max_price and _account contains more than
1000 pounds 7
The Renesas C compiler for the R8C has several additional logical operators that
can be used for bitwise operations on variables:
&
for bitwise AND operations
b a a A b
0 0 0
1
for bitwise OR operations
0 1 0
1 0 0
A
for bitwise XOR operations
1 1 1
Examples:
a =10011010
b = 11000011
a&b = 10000010
a =10011010
b = 11000011
a|b = 11011011
a =10011010
b = 11000011
a A b = 01011001
Shortcuts
Americans are masters at inventing shortcuts. That’s especially true for Dennis
Ritchie and Brian Kernigham, the inventors of the C language. Many programmers
type in their programs using the ‘hunt-and-peck’ system, so they try to avoid any
unnecessary typing effort.
Shortcut
Normal
Shortcut
Normal
a*=b
a = a*b
a«=b
a = a<<b
a/=b
a = a/b
a>>=b
a = a>>b
a+=b
a = a+b
a&=b
a = a&b
a-=b
a = a-b
a|=b
a = a|b
a%=b
a = a%b
XJ
II
<
cc
a = a A b
a++
a = a+1 (increment)
a-
a = a-1 (decrement)
Example:
for(t=0, t<1 00000, t++); /* timer loop 7
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elektor electronics
Functions in C
The function concept
Functions are the essence of the C programming language. A function can be
called from the main routine or from any other function. Every C program must
include at least one function, which is called main() . It is automatically called
when the program is started.
Functions are individual program segments (blocks) that perform specific activities
(operations), such as the familiar operations performed by pocket calculators:
CE clears the input memory of a pocket calculator. In C, it would be described
as a function that does not require any numerical input (parameters) and does not
return any sort of number.
expects to receive a number as input in order to calculate its inverse value.
In C, this is described as a function with an input parameter.
+ * / , by contrast, requires two parameters as input, and S ,
the summation function, requires several parameters.
sin and log , on the other hand, are functions that require one input
parameter.
Declaring a function
The general form of a C function is:
type function_name(type varl.type var2,type var3,...)
r \
return
type
input parameter with
type declaration
Examples:
A function with no input or output parameters:
void wait_1(void)
asmfnop"); // Call no operation in assembly language
The word void tells the compiler that the function wait_1 does not require any
input parameters and does not return any result. The void keywords can also be
omitted:
wait_1 ()
asmfnop");
elektor electronics
13
If a function contains more than one instruction, the instructions must grouped into
a block by enclosing them in curly brackets ( { } ). In that case the semicolon at
the end must be omitted.
wait_2()
{
no
asmfnop")
asmfnop")
asmfnop")
no
// Wait three times
A function with an input parameter but no return parameters:
int t;
wait_3(int several_times)
for(t=0;,t<= several_times;t++);
/* The for loop increases the value of t stepwise
(increments t) starting from 0 until it reaches the
value of the input several_times (time delay) 7
A function with input parameters and a return parameter:
float _volume(float length, float width, float height)
return length*width*height;
/* This function expects three inputs, which are stored
in the variables length, width and height. The product
of these three variables is then calculated and returned
to the caller as a floating-point number 7.
Calling a function
Functions are called by simply stating their names. This can be done at any
location in the program. After the function has been processed, which can be
recognised by the ; in case of a function containing only one instruction or the
curly bracket } in case of a function containing several instructions, a return to the
calling location occurs automatically. The keyword return has a different
meaning in C than in assembly language. In C, it designates the return value
instead of the end of a subroutine or function.
Multiple-level function nesting is allowed. ‘Function nesting’ means that one
function calls a second function, which in turn calls a third function, and so on.
14
elektor electronics
Examples:
Calling a function from the main routine without any input or return parameters:
void main(void)
{
wait_1();
}
Calling a function from the main routine with an input parameter but no return
parameters:
void main(void);
{
wait_3(100);
}
// The constant 100 is passed to function wait_3
Calling a function from the main routine with input and return parameters:
void main(void);
{
no_of_litres = _volume(a,b,c);
}
/* The values of the variables a, b, and c are passed to the
function _volume. The function then calculates the volume of
a body and returns the result to the variable no_of_litres.
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15
Program Control
if
It frequently happens that an instruction or block of instructions should only be
executed if a certain condition is satisfied. A condition is satisfied if a test of the
condition returns the value true . Every number except zero is regarded as
true ; zero is regarded as false
If several instructions are to be executed when the condition is satisfied, they must
be grouped into a block.
if (condition)
{
statement_1
state ment_2
state ment_3
II ...
if(button == 3)
redjed = _on;
if(button == 3)
{
grnjed = off;
redjed = _on;
}
if.. .else
If one instruction or block of instructions is to be executed when a condition is
satisfied, while an another instruction of block of instructions is to be executed
when the condition is not satisfied, an if... else conditional state men t is
used.
The general form is:
if (condition) statement_1 ; else sfatement_2 ;
sfatem
If several instructions are to be executed, they must be grouped into a block.
16
elektor electronics
Examples:
if(button == 3)
redjed = _on;
else
grnjed = _on;
if(button == 3)
{
grnjed = _off;
redjed = _on;
}
else
grnjed = _on;
3
if(button == 3)
{
grnjed
redjed
}
else
off;
on;
grnjed = _on;
redjed = _off;
}
switch
If a conditional statement has more than one or two possible outcomes, it is very
tedious to implement it using the if... else structure. In that case it’s better to
use the switch /case structure with multiple alternatives. This type of program
control can be compared to a rotary selector switch with multiple positions (cases).
The general form is:
switch (variable)
{
case
constant_1 ;
instruction^
break;
case
constant_2;
instruction_2
break;
case
constant_3;
instruction^
case
II ...
break;
default
instruction_x;
The switch function compares the content of variable to the value of a
constant (COnstant_x ) for each of the defined cases (case ). If the result of
the comparison is positive, the corresponding instruction (instruction_x ) or
elektor electronics
17
block of instructions is executed. Program control returns to the caller of the case
statement when the break keyword is reached. If none of the cases listed in the
case statement is found, the instruction following default is executed. The
default portion can be omitted if it is not necessary.
Example:
switch (_button)
{
case 1 :
redjed = _on;
break;
case 2:
yeljed = _on;
break;
case 3:
grnjed = _on;
}
default blu_led=_on;
may be
omitted
/* Enable the red LED if the value of _button = 1, the yellow
LED if it is 2, and the green LED if it is 3. If the variable
_button does not contain 1, 2, or 3 (e.g. 4), enable the blue
LED 7
for
A for loop is used if part of a program must be executed multiple times.
The general form is:
for(start_value; end_condition; step_size)
instruction^ ;
When the for loop is called, start_value is assigned to a previously defined
count variable. The count variable is then incremented or decremented by the
value of step_size each time the loop is executed, until the test of
end_COndition yields the logical value true .
If several instructions are to be executed, curly brackets ( { } ) must be used to
group them into a function block.
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elektor electronics
Examples:
int t;
for(t=0, t < 10, t++)
blink_led();
/* Integer variable t is assigned the value 0 when the for
loop is entered. Next, the function blink_led() is called.
After the first pass through the loop, the variable t is
incremented (t++) to the value 1 . As 1 is less than 10, the
process continues until t = 9. The loop is thus executed ten
times. 7
a = 2;
b = 10;
c = 4;
int i;
count variable
for(i = a; i < b; i+ = c)
{
red Jed = _on;
red Jed = _off;
}
/* This loop is executed only two times. 7
while
A while loop is used when execution is tied to a condition.
The general form is:
while(_condition)
{
instruction^ ;
instruction_2;
II ...
When the while loop is called, the value of the condition (_condition) is first
tested. If the result is positive (true), the instructions (instruction_x ) are
executed repeatedly until the result of the test is false.
elektor electronics
19
Example:
#define true 1
while(i == true)
{
i = button_pressed();
blink_led();
/* The function blinkjed is executed until the function
button_pressed no longer returns the value 1 to variable i.
do. ..while
A while loop will not be executed if the condition is not satisfied at the
beginning of the loop. If it is necessary for instructions to be executed at least
once, the condition must be tested at the end instead. A do. ..while loop is
used in such cases.
Example:
#define true 1
do
{
i = button_pressed();
blink_led();
}
while(i == true);
A — ,
/* The function blink led is executed at least once 7
20
elektor electronics
Appendix
Header file sfr_r813.h
The header file sfr_r813.h provides access to the special function registers
(SFRs) of the R8C microcontroller. These registers contain the basic settings for
the microcontroller, such as the port directions (in/out), timer settings, A/D
converter settings, UART settings, and so on.
The R8C microcontroller has more than 50 SFRs. That means we have to limit
ourselves here to a selection of the most important SFRs. Refer to the R8C/13
Group Hardware Manualor detailed information on all of the SFRs.
Port registers (P0, PI, P2, P3 and P4)
A port is a memory location that is connected to the pins of the microcontroller and
is thus externally accessible. Ports are used for inputting and outputting data. A
port can be either an input or an output. When the microcontroller is started up, all
ports are configured as inputs by default. The direction (input or output) can be
changed using the Port Direction (PD) registers.
The following example shows how to change the port direction:
Examples:
pdl = OxOF;
)* portl , bits 0:3 = output
bits 4:7 = input 7
pd2_3 = 1 ;
/* port2,bit3 = output 7
pfrrl Oredwt RBgiSlW pdl
<■0. l-i3LJ
*7 bd fcfli&a b2 bl bti
d |d |d b I,* |d |d | d
3-5 nfeji &r1 hfl>/
... and the following example shows how to output data via a port:
Pori Hogwtorek
1
I-*. 1 2 1. *
bl b6 b5 M
b3 b2 M bO
1
■ i ij Li [-M
9 d U * 1
1
Examples:
pi = OxOF;
/* portl, bits 0:3 = 1
bits 4:7 = 07
pd2_3 = 0;
/* port2,bit3 = 07
/* If a 1 is written to a port register, the supply voltage (e.g.,
+5 V) will be present on the corresponding pin. A 0 causes the pin
to be at ground potential (0 V) 7
elektor electronics
21
Protection registers (PRCR)
The PRCR registers can be used to protect the contents of other important
registers against overwriting (if the program goes out of control, for instance).
P rowel Register PRCft Examples:
prcO = 1 ;
System Clock Control registers (CM1, CM2 and OSD)
The R8C microcontroller has two oscillators to provide the clock for the CPU. One
oscillator is internal and is called ‘on-chip oscillator’, while the other is external and
is called ‘main clock’. The ‘main clock’ oscillator uses a quartz crystal connected to
the Xin and Xout pins.
The CM registers determine how the microcontroller clock signal is generated. In
addition, a prescaler can be enabled and configured to reduce the frequency of the
processor clock.
System Qodk Control Register
CMi
b7
b&
b5
b-4
bi m
::n
1 °
_eJ
3
jiL
c
c
external crystal
oscillator mode
Examples:
cm13 = 1;
/* Xin/Xout on ports p46 and p47
= ext. xtal 7
cm15 = 1;
/* Xin/Xout driver high 7
cm16 = 0;
/* prescaler for CPU clock 7
cm17 = 0;
/* prescaler for CPU clock 7
Sy&ienn ciosh CoiMral H&p&le'
CMD
b7 m tin- t>a , b2 bs K!
Examples:
cm05 = 0;
/* enable Xin/Xout on ports p4.6
and p4.7 7
cm06 = 0;
/* enable prescaler 7
CM1 prescaler
bits 6 & 7 set
cyrstal oscillator enabled
22
elektor electronics
The Oscillator Stop Detection (OSD) register is used together with the other
registers to select the clock source, and it is also responsible for monitoring the
clock signal.
Obciiiaidf Stop Detection
OSD
Examples:
osd2 = 0;
/* enable external xtal osc. as
CPU clock source 7
osd2 = 1;
/* disable external xtal osc. 7
Header file math.h
The header file math.h contains the library of mathematical functions for the
R8C. Here we describe some of the most important functions.
Functions of type double Functions of type float
f_name(double x); f_name(float x);
sin();
sqrt();
sinf();
sqrtf();
cos();
cosf();
powf();
tan();
exp();
tanf();
log();
expf();
asin();
Iog10();
asinf();
logf();
acos();
acosf();
log 1 0f();
atan();
mod();
atanf();
sinh();
fabs();
sinhf();
fabsf();
cosh();
floor();
coshf();
floorf();
tanh();
ceil();
tanhf();
ceilf();
Functions of type double
f_name(double x, double y);
Functions of type float
f_name(float x, float y);
powf();
atan2f();
fmodf();
pow();
fmod();
atan2();
fmod();
elektor electronics
23
lectronics
Microcontroller
Basics
Microcontrollers make things
possible that vastly exceed
what could be done previous-
ly. Innumerable applications
show that almost nothing is
impossible. There’s thus
every reason to learn more
about them, but that raises
the question of where to
find a good introduction to
this fascinating technology.
This book clearly explains
the technology using various
microcontroller circuits and
programs written in several
different programming
languages. In the course
of the book, the reader
gradually develops increased
competence in converting
his or her ideas into micro-
controller circuitry.
Microcontroller
Basics
ISBN 0-905705-67-X
230 Pages
£18.70 (US$ 33.70)
Elektor Electronics
(Publishing)
Regus Brentford
1000 Great West Road
Brentford TW8 9HH
United Kingdom
Tel. +44 (0) 208 261 4509
Fax +44 (0) 208 261 4447
More information on www.elektor-electronics.co.uk
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